Sir Keir Starmer was tonight accused of breaking Commons rules over his relationship with controversial chief of staff Morgan McSweeney.

The Conservatives said the Prime Minister may have broken the MPs’ code of conduct by failing to declare past support from the Labour Together think-tank, previously run by his chief of staff.

Mr McSweeney is facing questions about why he hid more than £700,000 in donations to the think-tank – which played a key role in Labour’s election campaign.

Labour Together has repeatedly boasted about the role it played in helping Sir Keir win the Labour leadership in 2020 after the party’s crushing election defeat the previous year.

But official records show Sir Keir did not declare any support from the group in the official Commons register.

Downing Street today refused to answer questions about Mr McSweeney’s time at Labour Together.

But the PM’s spokesman said Sir Keir had ‘full confidence’ in his chief of staff despite the controversy. 

Tory chairman Kevin Hollinrake urged the Government to ‘come clean’ about the support Sir Keir received during Labour’s leadership contest.

Mr Hollinrake said: ‘Not only are there very serious questions about McSweeney’s role in a cover up of donations used to install Starmer as leader of the Labour Party… but now it emerges the Prime Minister himself has not declared any of the support he received from Labour Together.’

He added that Sir Keir must ‘come clean’ about ‘what support he has received, and why he has failed to properly and transparently declare it’.

The think-tank has boasted that it ‘helped rally the party membership behind Keir Starmer’ in his battle to succeed Jeremy Corbyn as leader.

The role played by Labour Together in Sir Keir’s rise was detailed in a book last year by journalists Patrick Maguire and Gabriel Pogrund. 

It revealed Sir Keir received access to polling data worth hundreds of thousands of pounds to aid his campaign.

Under the Commons code of conduct MPs are required to declare any support worth more than £1,500 designed to help their ‘candidacy at an election for parliamentary or non-parliamentary office’.

Labour Together was fined £14,250 by the Electoral Commission in September 2021 for more than 20 breaches involving the £700,000 in undeclared donations, which was blamed on ‘human error’.

A spokesman for the think-tank said it had cooperated with the probe, which came after Mr McSweeney quit. 

The Tories have now asked the Electoral Commission to reopen the investigation and refer it to the police.