MPs are returning to Westminster after the long summer break to find the expenses row still rumbling on.
The parliamentary sleaze watchdog is due to reveal whether former Home Secretary Jacqui Smith, whose case was among the first to provoke the public's fury, will face punishment.
Meanwhile, scores of MPs - including Gordon Brown - are expected to be sent letters by auditors asking them to repay money from the past five years.
Mr Brown could be asked to repay more than £5,000 in expenses, including claims for cleaning his London flat and constituency home, The Daily Telegraph reported.
There are signs that many could choose to fight the findings of the review led by former civil servant Sir Thomas Legg, with a senior MP warning that his colleagues will not tolerate being treated "unfairly".
Sir Stuart Bell - who sits on the ruling Commons Members Estimate Committee (MEC) - said: "The MPs will have in their breast pocket a letter from Sir Thomas dated the 2nd of July saying that his review will be carried out in accordance with the rules at the time and the standards that applied at the time over the past five years...
"I think many MPs, if they read the newspapers, may feel (Sir Thomas) is not staying within that remit, he's not respecting the decisions that were made by the fees office in accordance with the rules at the time."
The Labour MP also hinted that the MEC could overturn any punishments that were not "fair and just", adding: "If there is suggestion that Sir Thomas is not abiding by the rules and standards at the time, I think the public would accept that some breach of fairness there is not actually proper for our Members of Parliament."
Downing Street is braced for the Prime Minister to be asked to return some of the money spent on a cleaner for his private flat in London. Although there is no suggestion of impropriety, the move would be particularly embarrassing as Mr Brown personally insisted on the re-examination of all claims. Aides to the premier indicated he would abide by the findings.
The letters will be sent out privately, and Sir Thomas is not expected to deliver his final report until December.