MPs have been accused of "marking their own homework again" after a parliamentary watchdog cleared former Tory minister Peter Lilley of wrongdoing over undeclared financial interests.

The Labour MP who reported Mr Lilley to the Commons Committee on Standards said that the finding was a "Maria Miller Part Two".

Mrs Miller, the former Culture Secretary, resigned amid public anger over her expenses.

But the case prompted intense debate over the ability of the Standards Committee, which had investigated Mrs Miller, to hold MPs to account.

Recently a report by the committee found Mr Lilley not guilty of intentional wrongdoing.

The Hitchin and Harpenden MP was investigated after he failed to declare his position as a director of an Asian-based energy company in two debates in Westminster Hall, a parallel debating chamber to the Commons.

Mr Lilley insisted that both debates were about the UK and his interest had "no bearing on UK energy policy, which has no impact on Tethys Petroleum Limited's activities or profitability."

Parliamentary rules state that it is "the responsibility of the Member, having regard to the rules of the House, to judge whether a financial interest is sufficiently relevant to a particular debate, proceeding, meeting or other activity to require a declaration."

The Standards Committee found that previous declarations of potential conflicts of interest by Mr Lilley demonstrated "a willingness to declare when he judged it relevant."

Their report stated: "We do not think it would be fair to Mr Lilley to find him in breach of a rule which was not clear at the time he considered the matter.

"It would be inappropriate for us to criticise Mr Lilley or suggest further action in this case."

But Thomas Docherty, the MP for Dunfermline and West Fife, who first reported Mr Lilley to the committee hit out at the finding.

He said: "This demonstrates once again the failings of the Standards Committee, which will again lead to accusations of MPs marking their own homework.

"The sooner we remove the government majority and introduce a majority of lay members on this committee the sooner the public can have confidence in it".

He added: "This is Maria Miler Part Two."

A spokesman for the committee declined to comment last night, although she pointed out that there are three lay members of the committee.

Labour have pledged to reform the Standards Committee.