Leading article: Hain must go. No ifs, no buts

Peter Hain's attempt to "get on with my cabinet jobs" is unlikely to succeed. The Secretary of State for Work and Pensions – and Wales – admits that he has broken the law, by failing to declare on time £103,000 of donations to his campaign for the Labour deputy leadership. Curiously, the law is unclear about the penalties for late disclosure, but Mr Hain is also being investigated by the Parliamentary Standards Commissioner. The failure to declare funding is, almost by definition, also a breach of Parliament's rules on the Register of Members' Interests.

The most severe penalty the Commissioner can impose would be to suspend Mr Hain from membership of the Commons. By convention, he would not continue to serve as a minister if he were censured in this way. But the Prime Minister could save time, embarrassment and a modicum of honour by inviting Mr Hain to leave the Government forthwith.

Mr Hain's best line of defence might have been that his campaign for the deputy leadership was miserably unsuccessful. His political career could hardly be said to have gained from the money raised so chaotically. That would have been beside the point, but at least it would have shown a little of the self-deprecating humour that can sometimes get a politician out of a tight spot.

Mr Hain's excuses have been as lacking in credibility as they have been in humour. When he published what he called "full details" of his undeclared donations last week, he said: "I gave my campaign for office within the Labour Party second priority to my government responsibilities." "I was busy" is not an excuse normally accepted by a court. Nor is it one accepted by his own Work and Pensions Department, which runs a poster campaign declaring: "No ifs, no buts: benefit fraud is a crime."

The important part of Mr Hain's statement last week was his claim that "immediately I became aware on 29 November 2007 that these donations had not been declared within the required timescale, I took steps to inform the Electoral Commission". This was stretching the truth. What he said on 29 November was that he had failed to register a donation of £5,000 from Jon Mendelsohn, the man later brought in by Gordon Brown as chief Labour Party fundraiser – a donation, incidentally, that does not appear on the "full" list Mr Hain published last week. It was not until 3 December that he admitted there were further donations that had not been "registered as they should have been", and that he would make a full declaration in due course. In both cases, his statements were prompted not by answers he solicited from his campaign team, but by journalists' questions.

Mr Brown's attempt to push funding irregularities into a box marked "Tony Blair is history" makes it particularly important to take a firm line with Mr Hain. Especially after a week in which Mr Blair and large sums of money have again been in the headlines, albeit in the different moral context of the former prime minister's private earnings. Mr Blair took an aggressive approach to Labour Party finance in which ends justified means.

At the start of his premiership, it simply failed to occur to Mr Blair that there might be a conflict of interest between Bernie Ecclestone's £1m donation and government policy on tobacco advertising. Towards the end of his time, he thought he could get away with circumventing his own laws to take secret loans from people he would later try to put in the Lords. This newspaper claims some of the credit for the failure of the cash-for-honours scam, and we thought Mr Brown had learnt the lessons of his predecessor's cavalier approach.

So he had, but the re-education process has been imperfect. The story of the £600,000 given to Labour by David Abrahams through intermediaries revealed that some of the personnel and practices of the Blair era had been allowed to continue into the Age of Change. Mr Brown found his coat was snagged on two hooks that might have implicated him in the culture of his predecessor.

One was Harriet Harman, whose successful campaign for Labour's deputy leadership, with Mr Brown's discreet support, took £5,000 from a third party without realising it came from Mr Abrahams. Her "honest mistake" defence was credible enough. The other was Mr Mendelsohn, who knew about Mr Abrahams's unconventional funding when he arrived at Labour HQ, and said that he had been intending to straighten it out when the story broke in November. It was a less convincing excuse than Ms Harman's, but for want of evidence to the contrary, it was only fair to give him the benefit of the doubt.

Mr Hain's casual attitude to his campaign finances provides a third hook on which Mr Brown may find himself and his government held back by the culture of the Blair years. In order to make a clean break, Mr Hain must go.