MPs have been warned to brace themselves for more expenses scandals amid increasing calls for Culture Secretary Maria Miller to resign.
Commons leader, Conservative Andrew Lansley, warned it was "over-optimistic" to think there would be no further cases.
Betty Boothroyd, the former Labour Speaker of the House, added her voice to those calling on Mrs Miller to go, saying she was bringing Parliament into disrepute.
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Mrs Miller's party colleagues were also increasingly vocal about her position. London MP Zac Goldsmith, said he was surprised she had not yet resigned.
Mrs Miller herself broke her silence to admit she had let her constituents down.
In a column in her local newspaper, the MP said she was "devastated" about the criticism she received last week from the Commons Standards Committee.
She said the last 16 months of investigation into her expenses had been "difficult", adding: "I have unreservedly apologised for the way I handled and approached the inquiry ... I am devastated this has happened, and that I have let you down."
Her parliamentary aide Mary MacLeod said Mrs Miller was the victim of a witch-hunt because of her role in the Leveson inquiry into press standards. However, the aide was later forced to admit she had no proof to back up that claim.
Last week a report by the independent Parliamentary Standards Commissioner found Mrs Miller should repay £45,000 was watered down by MPs on the Commons Standards Committee.
They ordered her to repay £5800 and apologise to MPs for her attitude to the investigation into her expenses.
Mrs Miller's apology lasted 32 seconds.