Families of the victims of the 7/7 London bombings may be barred from parts of the inquest as the government seeks to hold the hearings behind closed doors.

According to leaked home office documents, ministers may use new powers under the counter terrorism bill to stop families hearing evidence that could jeopardise national security or affect relations with another country.

The new powers also allow the home secretary to appoint the coroner and prevent a jury from being involved.

According to the documents given to a Sunday newspaper, the government is delaying the inquest until the counter terrorism bill becomes law.

The inquest could discover how terror leader Mohammed Siddique Khan was able to carry out the attack despite being under MI5 surveillance.

The same rules will apply for the inquest into the shooting of Jean Charles de Menezes in Stockwell underground station.

Fifty-two commuters [allegedly] died when three suicide bombers led by Khan detonated explosives on three Tube trains and a bus on July 7, 2005.

But a ministry of justice spokesman said: 'It would be unhelpful to speculate on whether the measure would be used in any given inquest. But the measure would be potentially available for use in any inquest which the secretary of state considered would involve material that could not be disclosed publicly without harming the public interest.'

The home office denied the hearing was being delayed until the bill was passed, and insisted the delay was due to a criminal trial on the bombings which must be completed before the inquest.

John Falding, whose girlfriend Anat Rosenberg was killed in the bombings, said he hoped the measures would not be used to spare the government's blushes.

He said: 'Given the government's track record, it suggests they've got something to hide. It would anger me if it was the government trying to get itself off the hook.'