Former Labour minister for Europe Denis MacShane is likely to avoid prosecution for fraudulent expenses claims, because the letters in which he admitted his wrongdoing cannot be used in evidence.

The parliamentary privilege rule, which guarantees MPs immunity from civil or criminal liability for actions done or statements made related to their duties as a legislator, prevents the letters being used as proof in any prosecution related to the scam, which lasted four years.

Earlier, MacShane, the MP for Rotherham, quit his position following a parliamentary committee finding that he had wrongfully claimed more than £12,000 to fund train travel around Europe.

Parliamentary standards commissioner John Lyon found the MP had entered 19 false invoices from a body called the European Policy Institute. The invoices claimed for expenses related to research and translation services from EPI, which was in fact a false organisation with no office and no salaried staff.

Faced with a 12-month suspension from the House of Commons and Labour Party hints that his career was over, MacShane resigned immediately, triggering a by-election for his now-vacant seat.

Conservative MP Philip Davies subsequently asked the Metropolitan Police to reopen its investigation into MacShane, which was dropped in July on advice from the Crown Prosecution Service. Davies claimed that Lyon's report on MacShane contained new evidence.

In his letters to Lyon, MacShane reportedly admitted his wrongdoings, but the letters are protected by parliamentary privilege.

MacShane previously accused the British National Party of running a campaign to put an end to his political career. BNP stalwart Richard Barnbrook lodged the original complaint against him, leading to the investigation by the Parliamentary Commissioner.

MacShane had claimed that he used the cash to fight anti-Semitism and the parliamentary committee ruled that he had made no personal gain from the money he fraudulently claimed.