Britain's Culture Secretary Maria Miller said Tuesday she was "devastated" by the furore over her expenses, as Prime Minister David Cameron faced increasing pressure to change course and sack her.
Breaking her silence after nearly a week of excoriating press attacks, Miller admitted she had let people down.
Her apology came after a fellow Conservative minister appeared to criticise Miller publicly and a prominent party backbencher said he was "surprised" she was still in her job, which includes overseeing a new system of press regulation.
More than 140,000 people signed an online petition calling for Miller to resign or pay back £45,000 ($75,400, 54,600 euros) on expenses related to her mortgage -- the amount a parliamentary standards committee said she owed before lawmakers cut it to £5,800.
Miller agreed last week to pay back the reduced sum and made a terse 31-second apology to parliament for providing limited information to an inquiry into her claims.
Writing in her constituency's local newspaper, Miller admitted it had been a "difficult" time.
"I have unreservedly apologised for the way I handled and approached the inquiry," she wrote in the Basingstoke Gazette.
"I am devastated that this has happened, and that I have let you down.
"I have already apologised and repaid an over-claim of my expenses, having myself drawn the committee's attention to the matter immediately as I was aware of it."
Cameron has given strong public backing to Miller -- one of four women in the Cabinet -- insisting she has "done the right thing".
Miller's parliamentary aide has also sent round a text urging colleagues to speak up in her favour, accusing newspapers of a "witch-hunt" due to her role in shaping a new press regulation system.
- 'A matter of honour' -
Two-thirds of Conservative party members believe she should stand down, according to a poll, because they fear the row is an unwanted distraction in the run-up to local and European elections next month.
Employment Minister Esther McVey on Tuesday broke ranks with Miller's cabinet colleagues, saying she would have handled the apology differently.
"I can honestly say it wouldn't be how I would have made an apology," the Conservative minister told ITV. "But different people have different styles and do things in different ways."
Backbench Tory MP Zac Goldsmith told the BBC: "I am surprised that Maria Miller hasn't stepped down. This is a decision for her to make or it is a decision for David Cameron to make."
Betty Boothroyd, a former speaker of parliament's lower House of Commons, said Miller should quit as culture secretary "as a matter of honour".
"She is bringing parliament into disrepute," the furious baroness said.
"I am very angry. I love parliament, I have cherished it, I have tried to develop it. I feel somewhat outraged that people treat it in this way."
Lawmakers' expenses became a toxic issue in the British parliament in 2009 when revelations by newspapers resulted in five members of the Commons and two members of the upper House of Lords being jailed for fraud.
There was support for Miller, with the Conservative London Mayor Boris Johnson saying she was being "hounded".
He blamed the system of expenses, saying a "proper independent system of evaluating what is owed" was needed, adding: "you cannot let the MPs do it themselves".
Cameron must face a potentially fraught meeting of senior Conservative backbenchers on Wednesday, which will give critics an opportunity to voice their frustration.