Margaret Ritchie, the MP for South Down and a former leader of Northern Ireland's Social Democratic and Labour Party, wrote to Mrs May two weeks ago asking for the inquiry to include an investigation into Kincora Boys' Home. There have been allegations for more than three decades that there was an official cover-up of the abuse of teenage boys at the Belfast home during the 1960s and 70s. Ms Ritchie said she expects an answer from Mrs May next week. Northern Ireland's First Minister, Peter Robinson, and Amnesty International have also called for Kincora to be included in the UK inquiry.

Last week, Lord Mayor of London Fiona Woolf was appointed to head the inquiry into allegations of organised child abuse at a wide range of institutions over many years. These include claims of abuse by senior public figures at Elm Guest House in south-west London.

She was chosen from 60 candidates after the resignation of Baroness Butler-Sloss following a row about the role of her brother, the former attorney general Sir Michael Havers, in potentially suppressing allegations of abuse.

It emerged yesterday that Ms Woolf, a corporate lawyer, will be given clearance to read classified intelligence documents from the time. It has been claimed that some MI5 agents were aware of cases of abuse but failed to act on the information. The most potent claims relate to Northern Ireland.

Simon Danczuk, the Labour MP who exposed the sexual behaviour of the late Cyril Smith, his predecessor in the Rochdale seat, is seeking a meeting with Ms Woolf. He said last night that the inquiry's terms of reference must include "some focus on Westminster".

"When I look at what Theresa May said when she announced the inquiry, there wasn't anything about politics and that's a cause for concern," said Mr Danczuk. "There needs to be a focus on whether there was a cover-up within Westminster, by which I mean within broader politics, party politics and Parliament."