If Keir Starmer resigns as UK prime minister and Labour leader, the UK does not go straight to a general election by default; instead there is a process inside the Labour Party and then a decision by whoever becomes leader about whether to call an election.

Immediate fallout

If Starmer resigned, he would be expected to:

  • Inform the King that he is resigning as prime minister.
  • Stay on as a caretaker until a successor is chosen, unless Labour MPs quickly coalesce around a replacement.
  • Trigger intense pressure inside Labour to agree a successor fast, to avoid a perception of chaos in government.

In political terms, his departure would deepen the current crisis around his leadership, which is already being shaken by the Epstein-related scandal and cabinet turmoil.

Choosing a new Labour leader

Labour has internal rules for leadership contests, which would govern what happens next.

  • A leadership race can be triggered if the leader resigns, or if enough MPs rally behind a challenger.
  • Candidates need a threshold of nominations from Labour MPs to get on the ballot, then members and affiliated groups normally get a vote.
  • Senior figures discussed in current speculation include Rachel Reeves, Angela Rayner and other cabinet heavyweights, each bringing different risks for Labourā€™s brand and electoral coalition.

Because Labour is now in government, there would be huge pressure to keep any contest short and orderly, rather than months of infighting.

What happens to the government?

The UK is a parliamentary system, so the governing party ā€“ not a directly elected prime minister ā€“ holds power as long as it can command a majority in the House of Commons.

  • If Labour MPs can unite behind one candidate quickly, that person could be invited by the King to form a government and become prime minister without a general election.
  • If the Labour Party splits badly, confidence in the government could collapse, raising pressure for an early election or a formal confidence vote in parliament.
  • Opposition parties would use the turmoil to argue Labour has lost its mandate and that the public deserves a say.

A historical parallel is how ruling parties have swapped leaders midā€‘term before (for example, Conservatives changing leaders while staying in government), but doing so in the middle of a scandal is riskier.

Impact on Labourā€™s future

Commentators are split on whether Starmer going would save Labour or sink it.

  • Some argue a new leader could ā€œresetā€ the government, draw a line under the Epstein fallout and try to rebuild trust before the next election.
  • Others warn that a brutal leadership contest could expose deep internal divisions, scare swing voters and hand momentum to Nigel Farage-style populist challengers or the Conservatives.

In the short term, markets and international partners would mainly look for signs of basic stability: a clear successor, a steady economic policy line, and no prolonged vacuum at the top.

Why this is trending now

Pressure on Starmer has surged because of:

  • The Epsteinā€‘related controversy around his appointment of Peter Mandelson as US ambassador.
  • Public criticism and calls to resign from senior Labour figures, including Scottish Labour leader Anas Sarwar.
  • Media and online speculation gaming out ā€œwhat if he quits?ā€ scenarios ā€“ some of it very dramatic, especially on political YouTube channels.

So when people ask ā€œif Keir Starmer resigns what happens,ā€ they are really asking whether Labour can change leader in time and in an orderly way, without losing control of the political narrative before the next big set of elections.

Is your main interest the formal Labour rules for choosing a new leader, or more the political drama and how it might change the next election?