MPs came under renewed pressure to accept demands for the repayment of taxpayer-funded expenses as Commons Speaker John Bercow warned they had to show voters they had "got the message".

Mr Bercow dismissed complaints about retrospective caps set down by Sir Thomas Legg's review and said colleagues had to take the consequences of "demonstrably wrong or extravagant" claims.

His demand came as it emerged HM Revenue and Customs are investigating whether 27 MPs broke tax law and it was suggested at least one MP could face criminal charges over the expenses scandal.

As the controversy continued to dominate Westminster affairs, the wife of one Tory MP also raised the prospect of legal action if an impending shake-up bars her from working for her husband.

In an interview for BBC Radio 4's The Week In Westminster, Mr Bercow defended the Legg review which has caused near-open revolt among MPs.

Critics say it is unfair to ask them to repay money claimed for cleaning and gardening when no caps were written into the rules, but Mr Bercow said that was "absurd". "Some limits must have been implicit," he said.

"The public has to see and be satisfied that we have got the message that there is public displeasure, that the process has to be changed and there there must be consequences for past claims if they can be shown to be demonstrably wrong or extravagant."

He went on: "If there are specific repayments that are expected by the Legg team, my strong expectation is that these payments will be made."

As multiple investigations of the pay and perks scandal continued, the Daily Mail said detectives believed they had sufficient evidence against Labour former minister Elliot Morley to send a file to the Crown Prosecution Service. Scotland Yard announced in June that it was launching full inquiries into several MPs and peers, understood to include Mr Morley who claimed £16,000 for a non-existent mortgage.

The Metropolitan Police would not comment on the report which came days after Home Secretary Alan Johnson failed to rule out the possibility of MPs going to jail.