Three labour MPs are arguing they cannot be prosecuted over expenses claims because they are protected by parliamentary privilege.
The trio – Elliot Morley, David Chaytor and Jim Devine – are being represented by a legal firm that has acted as solicitor to the Labour Party since 1990.
Their lawyers are understood to maintain that the Bill of Rights of 1689 makes them immune to prosecution. Police have forwarded files relating to the expenses claims of six MPs and peers to the Crown Prosecution Service.
Mr Morley and Mr Chaytor both claimed thousands of pounds for "phantom" mortgages they had paid off. Mr Devine submitted invoices for electrical work worth £2,157 from a company with an allegedly false address and an invalid VAT number. Steel & Shamash, a London legal company, confirmed it had instructed two QCs to consider whether the MPs should be protected by parliamentary privilege.
"It is their opinion that there are substantial legal and constitutional arguments that this is, in fact, the case," a spokesman for Steel & Shamash told The Sunday Times. "Any possible future involvement of the prosecuting authorities in this instance raises serious constitutional issues that will affect not just our clients but the way parliament itself operates."
A total of 400 serving and former MPs were yesterday reported to be facing demands to pay back some of their claims. They range from a few pounds to about £90,000. The number is twice as high as previously calculated.
The party leaders have instructed their frontbenchers to comply with repayment demands from Sir Thomas Legg, the auditor who has been scrutinising their expenses claims over the last five years.
However, 80 current MPs are appealing against Sir Thomas's demands and their resistance ensures the controversy will drag on until the general election expected in May. Those who lose their appeals and refuse to comply with Sir Thomas risk having the money deducted from their salaries, allowances or pension payments.
But the Commons authorities face a headache in dealing with former MPs, with little sanction other than appealing to their better nature or the expensive option of suing for the cash.