How could Keir Starmer be forced out of office?

Keir Starmer faced another huge blow today after losing his second senior aide in the space of 48 hours - triggering renewed calls he should stand down as Prime Minister.

But the Labour Leader appears to be clinging on despite the resignation of his press chief Tim Allan and Scottish Labour leader Anas Sarwar turning against him.

The under fire PM's judgment has been called into question over the Peter Mandelson scandal, with Mr Sarwar having already told Sir Keir to stay away from Scotland because he is politically toxic.

Labour figures are now in open revolt and an increasing number believe it is a question of when, not if Sir Keir will resign.

But with a spokesman today declaring the PM is not expected to quit - and will instead be focussing on the 'job at hand' - what are the options facing the Labour leader, and how could he be forced out of office?

Formal challenge

Under Labour's rules, a leader can be challenged if at least 20 per cent of the party's MPs nominate a single candidate to succeed him - on current numbers, this is 80 MPs. 

This would trigger a leadership contest in which other candidates could also try to gain enough nominations to stand. 

Sir Keir would be automatically on the ballot paper if he wanted to fight his corner. Only sitting MPs can be nominated, ruling out popular figures such as Andy Burnham. 

And, if his opponents remain divided, Sir Keir might even win the leadership contest, as Jeremy Corbyn did when he faced a similar challenge a decade ago.

Resignation

The Prime Minister could decide to quit of his own volition. Lord Blunkett suggested yesterday that Sir Keir was discussing his future with his wife Victoria this weekend, fuelling speculation he might resign. 

But allies say he feels a responsibility to carry on, believing that his departure could see Labour slide into the kind of instability that dogged the last Tory government. 

Attorney General Lord Hermer, the PM's closest friend in politics, recently described him as 'the most resilient person I have ever met'.

Women in grey suits

A delegation of senior MPs could attempt to tell Sir Keir that his time is up. 

Female Labour MPs have been particularly infuriated by the revelations of recent days. 

Potential candidates with enough authority include select committee chairmen Dame Meg Hillier and Debbie Abrahams, former minister Dame Anneliese Dodds and Parliamentary Labour Party chairman Jessica Morden. 

The drawback is that Sir Keir could simply ignore the warning.

Vote of confidence

Kemi Badenoch has offered Labour MPs the option of tabling a vote of no confidence in the Government. 

But such a move is unlikely to win support on the Labour benches as it would trigger a general election in which many are likely to lose their seats. 

Labour MPs could hold an informal vote of confidence among themselves, but Sir Keir could choose to ignore it.

Ministerial resignations

Ministers could attempt to bounce Sir Keir out of office by coordinating a wave of resignations to destabilise his administration.