The think tank that put Sir Keir Starmer into No 10 is now threatening to destroy him in what critics are calling a “scandal”. Labour Together worked tirelessly, but usually behind the scenes, to keep the Labour Party alive when Jeremy Corbyn was leader. Key figures included Morgan McSweeney, now Sir Keir’s chief of staff, and Steve Reed, now the Housing Secretary.

They prepared for the day when Mr Corbyn would be gone, and drew up plans to ensure he was replaced by a “moderate” leader who, they believed, could win a general election. The leader they chose was Keir Starmer. But now, Sir Keir’s relationship with Labour Together is coming back to haunt him. A new book has revealed fresh details, and Conservatives claim that Sir Keir should have declared the help and donations in the House of Commons Register of Financial Interests. They have asked the official Parliamentary watchdog, Standards Commissioner Daniel Greenberg, to investigate.

It threatens to be another huge blow for Sir Keir, after Deputy Prime Minister Angela Rayner was forced to resign over unpaid stamp duty.

But the Labour Together saga raises another important point, which isn’t about money.

The think tank was founded in 2015 (when it was called Common Good Labour), but really took on its current role as the vanguard of “moderate” and anti-Corbyn politics within Labour in 2017, when Morgan McSweeney took over as director.

However, it was only in 2019 that it adopted Sir Keir as its chosen candidate.

Some Labour MPs think this helps explain why the Government is floundering.

Tony Blair was one of the architects of the New Labour project that made him Prime Minister, alongside others such as Gordon Brown and Peter Mandelson.

Margaret Thatcher was, of course, a leading figure in Thatcherism, alongside people like Sir Keith Joseph.

But Sir Keir, more so than most Prime Ministers, was placed where he is by others. This may explain his extraordinary reliance on Mr McSweeney today, and what critics say is a lack of any discernible vision or guiding philosophy behind his government.

Conservatives are focusing on rules that state MPs must declare support any support worth more than £1,500. That could be a single donation, or multiple donations of more than £500 from the same source in the same year.

Donations can include cash, which the MP might spend on things like campaign materials or office costs, but it can also include other forms of support. For example, if you carry out a private opinion poll on behalf of an MP to give them information that helps them campaign, then they have to declare the cost of the poll.

A book called Get In by journalists Patrick Maguire and Gabriel Pogrund, about the rise of Sir Keir, has revealed details which the Tories say prove Sir Keir received help from Labour Together.

The book reports that Labour Together had “spent hundreds of thousands of pounds on YouGov polling” between 2016 and 2019.

Tories say the book also suggests the think tank provided a speechwriter for Sir Keir’s first speech as Labour leader.

In a letter to the Commissioner, Conservative chairman Kevin Hollinrake said: “Between January and April 2020, Labour held a leadership contest. Evidence from that period suggests that the Prime Minister accepted potentially thousands of pounds’ worth of advice and polling via the members’ association Labour Together. A review of his Register of Members’ Interests for that time reveals no record of these donations.

“The Parliamentary rules are clear that ‘support in kind’ from Labour Together should have been declared, but it was not.”

Labour Together has been in the spotlight before, when the it was fined £14,250 in 2021 for failing to report almost £740,000 in donations.

The Electoral Commission found more than 20 breaches of electoral law, with officials concluding failures occurred “without reasonable excuse.”

Mr Hollinrake said: “This has all the hallmarks of yet another Downing Street cover-up.”

He said: “Now it emerges that Keir Starmer failed to declare the support he received from Labour Together – from secret polling to help writing his speeches and behind-the-scenes campaigning.

“This latest scandal strikes at the heart of the Prime Minister’s judgement and integrity. He must come clean and be transparent with the British public about the true extent of his relationship with Labour Together and why this financial support was hidden from the authorities.”