Headache for Burnham as Starmer performs final 'U-turn' and stands down as MP with Green leader poised to challenge for seat

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By SOPHIE CHURCH - POLITICAL REPORTER

Published: 17:45 EDT, 1 September 2026 | Updated: 20:03 EDT, 1 September 2026

Andy Burnham was dealt an underhand blow on Tuesday as his predecessor Keir Starmer resigned as an MP.

In a move that left Westminster reeling, Sir Keir tendered his resignation as Labour's MP for Holborn and St Pancras on the day Parliament resumed after the summer break.

And in a further headache for Mr Burnham, Sir Keir's shock resignation saw Green leader Zack Polanski poised to challenge Labour in the resulting by-election.

The ousted former PM had previously said he would remain on Labour's backbenches until the next election, but in a final parliamentary U-turn said on Tuesday that now was 'the right time' to resign.

Sir Keir issued a statement saying he would now focus on 'international affairs including defence, security, trade and technology in a fast-changing world'.

This came as the new Prime Minister returned to Westminster on Tuesday to face the scrutiny of MPs after a summer spent courting voters.

Andy Burnham was dealt an underhand blow on Tuesday as his predecessor Keir Starmer resigned as an MP

Sir Keir tendered his resignation as Labour 's MP for Holborn and St Pancras on the day Parliament resumed after the summer break

The Greens on Tuesday suggested Mr Polanski would now run for the London constituency after months of speculation about his designs on becoming an MP

But Sir Keir's resignation wrested attention away from Mr Burnham as he tried to win over MPs after the parliamentary break.

And he now faces a tough contest to hold Holborn and St Pancras against an emboldened Green Party – which made record gains in May's local elections in London thanks to Labour's vote crumbling.

The Greens on Tuesday suggested Mr Polanski would now run for the London constituency after months of speculation about his designs on becoming an MP.

When asked about the Green leader's intentions, a Green Party spokesperson said: 'Zack has always made it clear he would like to be a London MP. London has been his home for over 20 years.'

This followed Mr Polanski saying in April he would 'almost certainly' run in a future by-election in the capital – and even eyeing up Sir Keir's seat.

In an interview with la Repubblica, he said: 'If there's a by-election in London, I'll almost certainly be running depending on where it is.

He added this could include Holborn and St Pancras 'if Keir Starmer is going anywhere'.

Mr Polanski in June suggested he would be willing to co-operate or form a coalition with a Labour government led by Mr Burnham.

Commenting on the chances of a Green win in North London, director of polling firm More in Common Luke Tryl said: 'For Labour, this will be a real test of whether Burnham can actually unite the left in a real election and save their urban strongholds.

'For the Greens, it's a test of whether or not Polanski can recover from recent stumbles and recapture his momentum of early spring.'

Politics professor at the University of Manchester Robert Ford wrote on X: 'The seat has exceptionally high shares of non-white voters (66 per cent), graduates (51 per cent) and young ppl (47 per cent aged 16-39) – all groups that have swung Lab to Green in recent years.

'This could be a humdinger of a by-election.'

This comes as Andrew Feinstein, an independent who came closest to beating Sir Keir in Holborn and St Pancras in the last general election, suggested on Tuesday he would do a deal with the Greens to deny Labour victory.

He wrote on X: 'We must ensure that all progressive forces in Holborn & St. Pancras unite in order to deliver an MP who represents us & will work for us.

'An MP who is the antithesis of everything that Starmer stands for.'

Both Nigel Farage and Rupert Lowe on Tuesday confirmed they would stand candidates for the upcoming by-election for Reform and Restore Britain respectively.