Leading article: A clear line from Mr Clegg

David Cameron was widely praised for seizing the initiative when he took members of his shadow cabinet to task for excessive expenses claims and listed those who would be paying money back. But he is not alone in emerging with some credit from this furore. The Liberal Democrats' Nick Clegg has taken a clear and consistent line, which he represented forcefully again yesterday.

It is true that the Liberal Democrats, as a party, have been less embarrassed by their expenses than either Labour or the Conservatives. None of their outer London MPs took the second homes allowance to which they were entitled, which exempted them from the first wave of public opprobrium. And when their turn came around to be exposed, the claims seemed fairly tame and lacked the colourful details of either upwardly-mobile Labour or the Tory squirearchy. Or is it that, after almost a week of revelations, expense-abuse fatigue is finally setting in?

Mr Clegg's garden path and international phone calls, Chris Huhne's trouser press, even Sir Menzies Campbell's interior decoration, did not take the party anywhere near chandelier or swimming-pool territory. And as Liberal Democrat MPs duly queued up with their pledges to give the money back, Mr Clegg took a different tack from the other party leaders.

While accepting that second-home allowances had been exploited, he placed special emphasis on the issue of "flipping" properties and selling on. In so doing, he was absolutely right. MPs need to be realistically reimbursed for the additional cost of living in two places. But the untaxed windfalls some MPs have received from playing the property market at public expense are a scandal of quite a different order.

At Prime Minister's Questions, Mr Clegg challenged the other parties to support a ban on MPs using their second-home allowance for mortgage costs. He was met with defensive hedging. Whatever new system is finally introduced, however, must be designed so as to stop this scam. Profits from property purchased or improved at public expense should revert to the taxpayer. Unless this is done, it will be hard to believe that MPs have learned all the necessary lessons.