The bill to the taxpayer for former Prime Minister Boris Johnson’s Partygate inquiry lawyers has risen to £245,000.
The politician is being investigated by MPs over whether he misled parliament over parties held in Downing Street during lockdown and is facing calls to cover the legal costs himself.
Mr Johnson took his legal team - led by Lord Pannick KC - to a four hour-long televised meeting of the Commons Privileges Committee in March when he denied knowingly or deliberately misleading Parliament.
If they find him in contempt of Parliament, he could be suspended as an MP triggering a by-election in his Uxbridge and South Ruislip constituency.
Opposition parties have said Mr Johnson should pay his own legal fees given the millions of pounds he has earned since leaving number 10.
The latest register of interests for MPs shows he earned more than £5.5 million since standing down last year.
The BBC reported the Treasury did not sign off the decision to use public money to pay the bill - a move criticised by former civil servants.
Alex Thomas, who worked in the civil service at a senior level and is now director of the Institute of Government, said: “Payment of legal fees to the former prime minister in these circumstances would seem to set a precedent and is certainly contentious, so looks on the face of it to meet the test to require Treasury approval.
"I’m surprised that the payments were made at all - but also that they were signed off in this way.”
Former deputy prime minister Dominic Raab paid his own legal fees during his bullying inquiry.
Labour’s deputy leader, Angela Rayner, said the arrangement leaving taxpayers covering Mr Johnson’s "Partygate defence fund is not only without precedent but without justification".
She said Prime Minister Rishi Sunak "must explain why he failed to put a stop to this brazen scheme and take immediate steps to ensure his disgraced predecessor returns this money to the public purse".
The Liberal Democrats urged Mr Sunak to launch an investigation into Mr Johnson’s legal costs and "how this precedent has been set".
"Boris Johnson needs to pay back every penny to the public purse immediately," said Wendy Chamberlain, the party’s chief whip.
The National Audit Office (NAO), which scrutinises government spending, is examining the decision to cover Mr Johnson’s legal costs during the inquiry, including whether Treasury approval was sought.
A spokesperson said the watchdog had spoken to the Cabinet Office about the contract to hire Mr Johnson’s lawyers "as part of our standard audit procedures".
"The NAO will publish its report on the Cabinet Office’s 2022-23 accounts when the audit is complete, which we are planning to be this summer," a spokesperson said.
