Labour MP John Mann passed details about the unnamed prominent individual within his own party to police officers earlier this year, the MoS has learnt

A senior Labour MP has been reported to police by two fellow MPs over claims of child sex abuse, The Mail on Sunday has learned.

One of the informants, Labour MP John Mann, passed details about the prominent individual to officers earlier this year.

Then, a fortnight ago, a Conservative MP went to the same police force armed with information about the same individual, some of which had been provided to him by a former Government Minister.

It is believed to be the first time that a sitting MP has been scrutinised by any of the ongoing police investigations into child abuse, representing a further extension of the ever-widening sphere of historic sex allegations.

Mr Mann handed his information over to an ongoing criminal investigation into another public figure, which included links between that figure and the Labour MP.

The Conservative MP’s allegations about the MP, which date back to the late 1980s, include claims that the MP had been arrested for indecency in a public place with a minor – during which he is said to have assaulted the arresting officers.

It is claimed the MP had performed political favours for the owner of a brothel in his constituency in which men consorted with underage males.

The Conservative MP also made further allegations about drink-driving, assault and corruption involving the Labour MP.

A BBC News team, headed by a journalist who specialises in reporting on sex abuse crimes, is also understood to have had access to the information. The team, which has been granted significant resources by bosses, has already started interviewing potential witnesses about the MP. Director-general Tony Hall has been made aware of the special project.

Mr Mann, a former member of the Treasury Select Committee, has established a strong campaigning record on the issue of abuse, and last year he compiled a dossier of historic allegations which detailed claims against 12 former Government Ministers.

The Met Police are carrying out Operation Fairbank, an umbrella inquiry into historical child sex abuse claims involving politicians in the House of Commons and House of Lords and other leading public figures

Earlier this year Mr Mann claimed that the number of victims could reach ‘tens of thousands’.

He said: ‘The state can’t deal with the numbers of people coming forward. The police and social services cannot cope with the volume that’s there, even now. And we’re hardly at the beginning of people coming forward.’

There are a total of five police investigations under way across the country into historical abuse allegations, of which the main one is Operation Fairbank – the Met Police’s umbrella inquiry into historical child sex abuse claims involving politicians and other leading public figures.

The Independent Police Complains Commission are also investigating if there was an Establishment cover-up of the late Cyril Smith MP's abuse of boys

The police watchdog, the Independent Police Complaints Commission (IPCC), is also investigating claims that there was an Establishment cover-up over the abuse perpetrated by the late Liberal MP Cyril Smith, including threatening a police officer with the Official Secrets Act after he said he had found the MP with two teenage boys in 1988.

Twenty-three people have claimed they were abused by the Liberal MP, who died aged 82 in 2010.

The Commons and the House of Lords are featuring heavily in the investigations. Earlier this year, Scotland Yard officers contacted Lawrence Ward, the Serjeant at Arms, the Commons’ most senior security official, to ask him to search files kept on MPs.

Mr Ward told the officers that if they produced a warrant, they could enter the Commons to investigate the files themselves on a ‘case by case basis’.

Earlier this month, Justice Lowell Goddard finally opened the public inquiry into child sex abuse, vowing that ‘no one, no matter how powerful’ will be able to avoid its scrutiny.

The New Zealand judge – brought in to head the inquiry after her two predecessors resigned over concerns about their links to the Establishment – said it could take a decade to complete. Her works covers five key areas of society from ‘the corridors of power in Westminster to children’s homes in the poorest parts of the country’.

Another abuse campaigner, Labour’s Tom Watson, has called for the inquiry to be given full access to MI5’s secret files containing the names of offenders.

Last night, the police force which has received the information about the Labour MP said it was unable to comment on any ongoing investigations which had not included any arrests.