The decision to give a Labour donor a 10 Downing Street security pass is “deeply concerning”, the Conservatives have said as they seek to increase the pressure on the Government over Lord Waheed Alli’s access.

Lord Alli, who has donated more than £500,000 to Labour over the past 20 years and was the party’s chief fundraiser for the General Election, was given a pass to Number 10 despite not having a formal job there.

On Sunday, senior minister Pat McFadden said it had been a temporary arrangement to allow Lord Alli to attend political meetings, adding he no longer had a pass.

But shadow paymaster general John Glen has written to Simon Case, the Cabinet Secretary, to request clarification on who authorised Lord Alli’s pass, and when it was issued and rescinded.

A Downing Street pass should be a privilege reserved for those that require access for work

Mr Glen said in his letter: “A Downing Street pass should be a privilege reserved for those that require access for work, including civil servants and special advisers, not those requiring occasional access as is possible through the Visitor Notification System, without requiring a permanent security pass.

“It is therefore deeply concerning that a pass was granted to a Labour donor providing unfettered access to the heart of government after significant cash and non-cash donations were made to the Labour Party.”

Mr Glen also asked whether any other donors had received security passes for Number 10 and if any other temporary passes had been issued.

Speaking to Sky News on Sunday, Mr McFadden said: “I don’t think it’s unusual for people to have passes to attend political meetings if they need to do so.

“I don’t think he’s got the pass now, but he may have had one in the past.”

As well as donating to the Labour Party itself, television executive Lord Alli has made cash donations to senior Labour figures, including Prime Minister Sir Keir Starmer, whom he also provided with clothes and accommodation.

Reports about Lord Alli’s pass come amid a growing row over jobs in the Civil Service being given to Labour donors.

Ian Corfield, who has donated £20,000 to the party over the past decade, including £5,000 to Chancellor Rachel Reeves, was given a temporary job as the Treasury’s director of investment.

On Saturday, it emerged that Mr Corfield would now be working as an unpaid adviser rather than a salaried civil servant, and the Conservatives urged the Prime Minister’s ethics adviser to investigate his appointment.

Others with ties to Labour or Labour-supporting think tanks have also been appointed to Civil Service roles, prompting complaints from the opposition about the politicisation of the usually impartial bureaucracy.