Ministers may use powers to block MI5 disclosure on bombings

The Government said it would not launch a legal challenge to the coroner's ruling that she should investigate allegations that the security services failed to stop the largely Yorkshire-based suicide bombers, despite the ringleader being identified during surveillance.

But Home Secretary Theresa May reserves the right to launch a public inquiry and halt the inquests a hearing at the Royal Courts of Justice in London was told.

Coroner Lady Justice Hallett ruled in May that the inquests should examine whether security officials could have prevented the 2005 London bombings.

Families of the 52 innocent people killed in the attacks welcomed her decision.

They want to use the inquests to ask MI5 officials why they did not follow up plot ringleader Mohammed Sidique Khan, who like two of his fellow bombers was based in Beeston, Leeds, after he was witnessed meeting known terror suspects 17 months before the atrocities.

But the Security Service argues this is both unnecessary and impossible because doing so would require the disclosure of top secret intelligence files.

Jonathan Hall, counsel for the Home Secretary and MI5, have revealed that Ministers decided against launching a judicial review of the coroner's ruling.

He told her: "The decision is not to seek to challenge your decision on scope. And so far as public inquiries are concerned, the Secretary of State does not propose to initiate a public inquiry, although that cannot be ruled out as a possibility."

One option for MI5 would be to hive off questions about whether the bombings were preventable into a separate inquiry, which could examine secret documents in private.

Section 17A of the Coroners Act 1988, as amended in 1999, gives the Lord Chancellor power to adjourn an inquest if the death is being investigated by a public inquiry.

Lady Justice Hallett extracted a pledge that any Ministers who take a decision on turning the hearings into a public inquiry will have to read an assessment of the impact the move would have on the bereaved families and the work done by her inquest team.

The inquests will begin on October 11 and are expected to last for about four to five months, counsel to the inquests Hugo Keith QC announced today.

They will begin with an opening statement, followed by details of the four suicide bombers' journey to London.

Evidence will then be called relating to the scenes of the four attacks, first Aldgate, followed by Edgware Road, King's Cross and Tavistock Square.

MI5 warned that the process of blanking out sensitive information in documents held by MI5 and the Metropolitan and West Yorkshire Police would take a team of six or seven Security Service officers five months.