The deputy prime minister and first secretary of state
Beatrice Barr Catherine Haddon
What is the role of the deputy prime minister and the first secretary of state? And how do they differ?
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Institute for Government
Who is the deputy prime minister?

Unlike the US vice president, there is no constitutional deputy who automatically deputises for the prime minister or who would take over in the event the prime minister was incapacitated.

However, British prime ministers have sometimes chosen to ask another minister to act as their informal deputy. This de facto deputy has sometimes been given the honorific title ‘deputy prime minister’ but at other times has been the first secretary of state or the chancellor of the Duchy of Lancaster.

Deputy prime ministers have tended to play a more substantial role in Labour governments because the deputy Labour leader is elected by party members and so has their own power base.

The current deputy prime minister is Angela Rayner, who is also the elected deputy leader of the Labour party. Rayner is also currently secretary of state for levelling up, housing and communities.

What is the difference between deputy prime minister and first secretary of state?

The title of first secretary of state is used to indicate that the holder ranks below the prime minister but is more senior than other secretaries of state. It confers no automatic rights or responsibilities but can, though not always, coincide with a role deputising for the prime minister. As the most senior secretary of state, the first secretary will sit closest to the prime minister around the cabinet table.

There can also be a second or third secretary of state, but usually this informal rank is inferred from their position in the cabinet hierarchy rather than a title provided to them.

The title of deputy prime minister similarly confers no automatic rights and responsibilities. It is usually used either to give a title to the leader of the second party in a coalition government or to convey a seniority above the first secretary of state, either because a prime minister wishes to empower a particular minister or, mor usually, because a particular minister has insisted on the title. The deputy prime minister may actually deputise for the prime minister – at PMQs, on cabinet committees or elsewhere – but this is not guaranteed.

Lord Mandelson, who served as Gordon Brown’s first secretary of state from 2008¬–10, described the distinction in his Ministers Reflect interview:

"Gordon [Brown] wanted to name me as Deputy Prime Minister but First Secretary was inserted instead because I was in the Lords rather than the Commons. It didn’t matter to me and I tried to do a job."

How do ministers deputise for the prime minister?

There are a number of occasions on which the prime minister might wish to delegate some of their responsibilities.

Prime ministers have often asked deputy prime ministers or first secretaries of state to chair cabinet committees in their place. John Prescott chaired nine cabinet committees in 2006 while Thérèse Coffey chaired two during her brief tenure as deputy prime minister in 2022.

The deputy prime minister is often called upon to stand in at PMQs when the prime minister is away, although this responsibility can also fall to another senior minister. Dominic Raab frequently stood in for Boris Johnson and Rishi Sunak, first in his capacity as first secretary of state and then as deputy prime minister. The chancellor of the Duchy of Lancaster, David Liddington. frequently stood in for Theresa May, who never officially designated a deputy prime minister.

At other times, prime ministers have asked a close ally to act as a de facto deputy or ‘fixer’ and delegated aspects of their responsibilities to them. This might include chasing progress on key policies and, particularly, cross-cutting issues, brokering deals between departments and chairing meetings and committees. In recent years this role has been given to a minister based in the Cabinet Office, and therefore benefitting from the resources of the Cabinet Office and proximity to No10. Oliver Dowden was said to play such a role for Rishi Sunak and it has already been reported that the new Chancellor of the Duchy of Lancaster, Pat McFadden, will perform a similar function for Keir Starmer.

When the prime minister is on holiday, a senior minister is appointed to deal with day-to-day prime ministerial business. This is likely to be the deputy prime minister where there is a minister with that title, but it does not have to be.

Finally, when a prime minister is ill or incapacitated, another cabinet minister would usually be expected to take on some of the PM’s responsibilities. Unlike the US, however, there are no formal rules that govern this handover of power. In 2020, when then-prime minister Boris Johnson went into intensive care while suffering from Covid-19, it was then-first secretary of state Dominic Raab who took on his day-to-day responsibilities.

If a prime minister died in office, would the deputy prime minister take over?

Not necessarily. The UK has no automatic process for what happens if a prime minister dies or is incapacitated in office, although there are certain constitutional principles that would be followed. After Boris Johnson was hospitalised in 2020, the Cabinet Office considered what would be recommended practice in future, but this still does not amount to a constitutional rule.

The central constitutional principle is that a prime minister must be appointed by the monarch on the basis of commanding the confidence of parliament. There is no constitutional provision for an ‘acting prime minister’. The UK is formally governed by the cabinet who either exercise statutory and some prerogative powers in their own right, or who advise the monarch on how to exercise other executive powers. If the prime minister is incapacitated temporarily then the cabinet can advise the monarch in the absence of the prime minister.

A prime minister remains in post until they resign or otherwise vacate the role. In these circumstances, if the party in government had a majority in parliament then the requirement to command confidence would mean that the governing party would have to select a candidate with the support of its MPs. In practice, given that cabinet ministers are already acting as the monarch’s principal advisers, a replacement would likely be chosen by and from the existing cabinet, at least until a new leader of the party could be elected. This may be the PM’s deputy, but this is not guaranteed.

Is there always a deputy prime minister?

There is not always a deputy prime minister. In fact, the concept of a deputy prime minister is relatively new. Clement Attlee was the first deputy prime minister, serving during the wartime coalition from 1940–45. Between then and 2010, eight ministers deputised for the prime minister, but there were long periods without any deputy.

Since Nick Clegg’s appointment as deputy prime minister during the coalition, use of the title has become more common. There have been four deputy prime ministers and three first secretaries since 2015. This excludes Philip Hammond who was briefly and mistakenly appointed to the role in 2016. There were two periods between 2015 and 2019 where there was no appointed deputy prime minister or first secretary, although the chancellor of the Duchy of Lancaster performed a similar role for some of that period.

Sometimes there is both a deputy prime minister and a first secretary of state in one government. During the 2010–15 coalition government, Nick Clegg was deputy PM and William Hague as first secretary of state. Clegg’s title reflected his role as the leader of the junior coalition party and Hague’s title his status as a party ally of the prime minister.

Is there a department of the deputy prime minister?

The title of deputy prime minister or first secretary of state has usually been held by someone with another cabinet role and they have performed their role from an existing department.

Between 2010 and 2015, Clegg operated as deputy prime minister from the Cabinet Office and was provided with a larger team to support his responsibilities. He was also Lord President of the Council, a separate title that gave him responsibility for the privy council.

Some deputy prime ministers have had a team within the Cabinet Office alongside another departmental office. Between 2001 and 2006, John Prescott was supported by an Office of the Deputy Prime Minister, holding responsibility for the Social Exclusion Unit and Regional Coordination Unit, alongside his responsibilities in the Department for the Environment, Transport and the Regions.

How important is the role?

This depends on the circumstances of government. During the coalition, the deputy prime minister was unusually powerful because Nick Clegg was the most senior representative of the Liberal Democrats in government. His position was written into the coalition agreement, and some responsibilities were transferred from the secretary of state for justice to the deputy PM to increase his powers. He told our Ministers Reflect archive:

“I know the title was the same, but my role [as deputy prime minister] bore absolutely no relationship to John Prescott or Michael Heseltine. Because it was just a very brutal symmetry. The Coalition Government couldn’t do anything unless both sides agreed. So we had to set up from scratch something which Whitehall has never done before, and certainly has not done since, which is create a sort of two-headed, bicephalous way of making decisions.”

Outside of coalition, the relative strength of the deputy prime minister or first secretary of state depends on their relationship with the prime minister. As first secretaries of state Lord Mandelson and Damian Green were, in particular, known for acting as fixers for the prime minister, as was David Lidington as Theresa May’s Chancellor of the Duchy of Lancaster. Other prime ministers have relied on their chancellor as a second in command.