Amyas Morse carried out a “full scope audit” of £98.1m expenses paid in 2009-1 – the year of the expenses scandal.
The audit found the House of Commons authorities had failed to obtain receipts to justify £2.6m in claims. Another £11.3m of expenses had been incurred on items which MPs could not prove were necessary for parliamentary purposes.
The news came as David Cameron met with backbench MPs last night to discuss problems with the new system governing MPs’ expenses.
The Independent Parliamentary Standards Authority (Ipsa) has faced criticism from MPs that is not working properly and it’s too expensive.
Last night the Prime Minister agreed the new system was “anti-family” and would have to relax its grip by 1 April, or face being reformed.
A spokesman for Cameron added: “There needs to be a better system in place by 1 April otherwise it will have to change. That can be through Ipsa recognising its shortcomings, or it can be it being changed. Either way, it will have to change.”