Will there be a general election and what happens next after Starmer's resignation?
Labour leadership contest to follow this summer, but will the UK head back to the polls?
Wes Streeting has said he will back Andy Burnham to become the next Labour Party leader, after the former Greater Manchester Mayor put himself forward.
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Fresh from winning the Makerfield by-election, the MP has announced, to nobody's surprise, that he will try to succeed Sir Keir Starmer, after the prime minister resigned on Monday.
Former health secretary Mr Streeting had been tipped to stand himself, but in backing Mr Burnham he has ruled himself out of the race.
Here is what will happen from here as a new prime minister is chosen.
Read also: Emotional Keir Starmer pays tribute to family in Downing Street resignation speech
Who will be the next prime minister?
The next prime minister will be the next leader of the Labour Party.
A contest to decide this will be held over the summer if more than one candidate comes forward.
A new leader will be in place before Parliament returns in September.
Sir Keir will remain in post until the successor is chosen.
He said he will give that person his full support.
Which Labour MPs could run to be party leader?
Andy Burnham, the former Greater Manchester Mayor, was the first to declare he would run to be Labour Party leader - stating one hour after Sir Keir's resignation that he would throw his hat into the ring.
Former health secretary Wes Streeting, who had been tipped to run as well, has backed Mr Burnham.
Other possible candidates include:
- Shabana Mahmood: The home secretary and former justice secretary has been promoted under Sir Keir,
- Ed Miliband: Labour leader from 2010 to 2015, the energy secretary has restored his reputation as a cabinet member for Sir Keir,
- Angela Rayner: The former deputy leader is well placed to challenge to be the first ever female leader of Labour, and her northern success story is a draw for voters.