Liz Truss has been claiming from the £115,000-a-year (€133,000) public fund awarded to former UK prime ministers despite only serving for 49 days.
British Cabinet Office accounts released on Tuesday show that the Conservative MP claimed £23,310 (€27,034) in her first five months out of office.
It was understood she has continued to claim in the current financial year that started in April, but the sum will not be disclosed until next year’s report.
Ms Truss’ office declined to comment.
After she announced her resignation, Labour leader Sir Keir Starmer was among those arguing that Ms Truss should “turn it down” because of the brief time spent in No 10.
The Liberal Democrats’ Cabinet Office spokesperson Christine Jardine urged UK prime minister Rishi Sunak to “do the right thing and stop Liz Truss from claiming taxpayers’ cash from the ex-PM fund”.
“It’s an outrage that while families struggle to pay their bills and put food on the table, Liz Truss profits from her own failure,” she said.
“If Liz Truss wants to cut tax she should lead by example and stop taking hardworking British taxpayers for a ride by claiming handouts.”
The Public Duty Cost Allowance affords former UK prime ministers up to £115,000 a year to cover office and secretarial costs arising from public duties.
Sir Tony Blair and Sir John Major were the only former leaders to claim the maximum amount in 2022/23, though Gordon Brown was close on £114,627.
Ms Truss’ chaotic tenure in No 10 ended on October 25th after losing the support of Tory MPs.
On Monday, she defended her economic crisis-inducing mini-budget a year on from her chancellor Kwasi Kwarteng unveiling the £45 billion package of unfunded tax cuts.
She hit out at economists and “institutional bureaucracy” for her downfall as she hinted at further plans to intervene in Tory politics at the party conference next month.
The Cabinet Office accounts also detailed the total cost of Boris Johnson’s taxpayer-funded legal defence to the inquiry that found he lied to MPs over partygate.
The final cost was put at £263,079, in line with what the department had previously revealed.