Phillip Mawer, parliamentary commissioner for standards, has called for radical reform to the way MPs claim expenses.
There are currently large differences in what members of parliament claim for, with some MPs claiming almost £175,000 in expenses and others claiming less than £63,000.
As a result of these huge discrepancies, Sir Phillip has argued for stricter rules on expenses to restore public confidence.
"The degree of variation in the spend on stationery and allowances, and in some aspects of the travel regime, are not easily explicable," he said in an interview with The Times.
"It is so marked that it is bound to give rise to questions about members' practice."
In the latest report on expenses it emerged that Gordon Brown claimed £3,273 in stationery and postage, David Cameron claimed £7,672 and Menzies Campbell claimed £3,835.
However, other MPs spent as much as £25,000 on postage and £12,000 on stationery, raising concerns allowances might be being used for campaigning.
Last year MPs claimed £86.8 million in expenses - this is more than 50 per cent, or almost £30 million, higher than the amount which was claimed in 2002.
The average MP now claims more than £130,000 a year in expenses to go with their £60,277 basic salary and a generous pension. However, in most cases the majority of these expenses goes on staffing costs.
But Sir Phillip believes the sheer scale of the expenses claims and their rapid rise could lead to the public questioning them and potentially losing faith in the system.
"The focus has shifted," he told The Times.
"Looking back over the ten years or so that this current regime has been in operation, the spotlight initially was on cash-for-questions, that is paid advocacy.
"Then the spotlight shifted towards failure to register or declare interests. Now the spotlight is on allowances."
He called for MPs to provide receipts for any claim above £50, rather than the current level of £250, and added ministers with grace-and-favour homes should not have constituency properties funded as well.
Tighter rules should also be put in place for stationery, postage, newsletters and websites, the parliamentary commissioner for standards said. He also said politicians should cut their bills for free travel.