In a press conference in London at 11am on Friday, Director of Public Prosecutions Keir Starmer announced the results of an eight-month investigation into MPs’ expenses.

He said: “Following widespread concerns about the expenses claimed by some MPs and some members of the House of Lords, a number of complaints were made to the Metropolitan Police alleging criminal conduct.

“In light of these complaints on 15 May 2009, the commissioner of the Metropolitan Police, Sir Paul Stephenson, and I agreed to set up a panel of senior police officers and senior prosecuting lawyers to assess the complaints and consider whether there should be a criminal investigation into any of them.

“A careful and detailed police investigation followed in a small number of cases and by December 2009 the police had passed the files in six cases to the Crown Prosecution Service (CPS) to determine whether or not any charges should be brought.

“These files have been reviewed very carefully by senior prosecuting lawyers in the CPS, assisted where necessary by an external and highly experienced criminal QC.

“In four cases, we have concluded that there is sufficient evidence to bring criminal charges and that it is in the public interest to charge the individuals concerned. Accordingly, summonses in these cases have been obtained from the City of Westminster Magistrates Court and will now be served on the individuals in question.”

He then gave details of two charges against Elliot Morley, MP for Scunthorpe, three charges against David Chaytor, two charges against Livingston MP Jim Devine, and six charges against Conservative peer Lord Hanningfield, who is leader of Essex County Council.

Mr Starmer continued: “Lawyers representing those who have been charged have raised with us the question of Parliamentary privilege.

“We have considered that question and concluded that the applicability and extent of any Parliamentary privilege claimed should be tested in court.

“Can I remind all concerned that the four individuals now stand charged of criminal offences and they each have the right to a fair trial? It is extremely important that nothing should be reported which could prejudice any of these trials.”

l Following the announcement of the charges, Tory Leader David Cameron said he had asked Shadow Leader of the House, Sir George Young, to draft a Parliamentary Privilege Act which would clarify the rules on parliamentary privilege and prevent the principle being misused.

The Prime Minister’s spokesman said Mr Brown also did not believe that Parliamentary privilege was intended to cover issues of this nature.

He added: “If it proves necessary, the Government has said that it will legislate to clarify this.

“The Prime Minister's view is very clear — no MP is above the law.”