Meanwhile, MPs announced a formal inquiry into the London suicide bombings, which killed 52 innocent people, four years after the atrocity.

It will look for any common links between the bombers and those involved in other failed plots, both past and present in the UK, and will examine the Government emergency response system – the so-called COBRA meetings.

Graham Foulkes, from Oldham, Greater Manchester, whose 22-year-old son David was killed in the Edgware Road bombing, welcomed the move.

“I see that as really positive and I think it’s good news,” he said. “I would like an independent inquiry, but this is a very good second.”

The parliamentary Intelligence and Security Service Committee (ISC) carried out its own inquiry in to the bombings but its report in May sparked outrage when it said there was nothing MI5 could have done to stop the attacks.

The Home Affairs committee could begin its hearings as early as September but a witness list is still to be drawn up. It remains to be seen how forthcoming the security services will be in giving evidence or whether it will be held in private.

Patrick Mercer, a Tory member of the committee, said: “This will be the biggest inquiry in July 7 and terrorist incidents in Britain.

“What we are going to try is to look at the links between failed attacks before 7/7 and right the way through to the latest successful and unsuccessful attacks that have been plaguing our security services.”

Keith Vaz, the Labour chairman of the committee, added: “The Committee will be inviting MI5, MI6 and terrorism experts to give evidence with the aim of gaining a detailed picture of what the security services knew before 7/7, what, if anything, could have been done to prevent the attacks and the Government’s response to the attacks.”