Maria Miller row: Johnson calls for 'ethical' watchdog

Boris Johnson has called for a "proper, independent" ethical watchdog for MPs after a controversy over Maria Miller's expenses as a growing number of senior Conservatives failed to offer the culture secretary their support.

The London mayor said Miller had been "hounded" over her expenses claims but would not specifically say she should keep her job.

Miller was seen entering Downing Street just after 8am on Tuesday, where she attended a scheduled meeting of the political cabinet at 8:30am. She had refused to answer shouted questions from reporters outside.

She has been offered David Cameron's full support, but has aroused intense irritation about the row from some in her party, including the influential 1922 committee of Tory backbenchers.

Speaking on BBC Radio 4's Today programme, Johnson acknowledged there was little public confidence in a system that allowed a committee of MPs to reduce the amount she had to pay back. Miller was ordered to repay £5,800 in over-claimed mortgage expenses when an independent commissioner originally estimated that she should return £45,000.

Asked whether she should keep her job, Johnson said: "I don't know the facts of the case in great detail, but it seems to me she is being hounded quite a lot and my natural sympathies go out to people in hounded situations – how about that?"

He said the impact of the controversy on David Cameron's reputation was "frankly, an irrelevant consideration".

But he added: "The trouble seems to have arisen because you've got some discrepancy between what the independent assessor said and what the committee of MPs said. So let's get on with it and have a proper, independent system that everybody can have confidence in."

David Laws, a Lib Dem minister who resigned in 2010 over his expenses, was more direct in saying Miller "of course" has his support as a member of the government.

But a number of Tories have begun to distance themselves from her conduct, especially the tone of her short apology to parliament.

Esther McVey, a Tory work and pensions minister tipped for promotion, told ITV that Miller's 32-second Commons apology for over-claiming expenses was not how she would have done it herself, while Nicola Blackwood, a Tory aide in the business department, indicated that she would be "really quite worried indeed" if in the same position.

Jackie Doyle-Price, a backbench Tory, also told the BBC she would not expect support from her colleagues ahead of local elections if she were in a similar position to the culture secretary.

The pressure on Miller from within the Conservatives may come to a head at Wednesday's meeting of the 1922 committee. The prime minister met Graham Brady, the head of the committee, on Monday and the issue of Miller's expenses on the reputation of the party was brought up, sources said.

Lord Tebbit, a former Tory chairman, and a group calling itself Conservative Grassroots, have previously called for her to be sacked.

Throughout the furore over Miller's over-claimed expenses, David Cameron has said he wants her to keep her job. On Monday, he said the culture secretary had "done the right thing" at all times. However, the first slight crack in Cameron's position emerged when he acknowledged that there might need to be changes to the Commons standards committee, including giving a formal power of veto on its decisions to lay members.