The latest claims, published in The Sunday Times, suggest that investigators found a police-style tracking device in a car belonging to Mohammad Sidique Khan after he led the London bombings which killed 52 people.

If, as suggested, the bug was planted by Special Branch in a surveillance operation against Yorkshire Islamists, why did the authorities fail to stop Khan attacking London? Jacqui Putnam, who was in the next carriage to Khan in the Underground train he blew up at Edgware Road station, told The Times: “People should be asking these questions. We are just drifting. Everybody is terrified that people are going to lay blame.

“The way forward is to find out what went wrong. We are not looking for heads to roll. The important thing is that different departments had information that they did not pool.

“We haven’t got any room for macho attitudes that ‘We in Special Branch, or MI5, or MI6, have our little empire and we are not sharing it with anybody’. They have to have a mechanism to share this information. If they had done that, alarm bells would have rung very loudly.”

She is joining Rachel North, a survivor of the Russell Square bomb, to meet Mr Reid and Tessa Jowell, the Culture Secretary, soon after the first anniversary.

The Home Office says that it does not believe a public inquiry would add to understanding of the causes of the atrocities but would divert police and the security services from preventing others.

Ms North has collected nearly 800 names, including those of some survivors, on an online petition (http://rachelnorthlondon.blogspot.com) for a new investigation.

The Intelligence and Security Committee (ISC), which scrutinises the secret services, concluded that Khan and his accomplice Shehzad Tanweer did appear on the periphery of investigations. MI5 told the committee’s inquiry that none of the four attackers had been identified as potential terrorist threats. Neither MI6 nor GCHQ had come across them.

The Home Office account said that the bombers had shown little outward sign of potentially violent extremism, making them difficult for law enforcement agencies to identify as threats.

Ms North said: “It appears that information is coming out that wasn’t shared with the ISC that is being uncovered by further media investigations.

“The bombers were allegedly working alone and not part of any radicalised group. Yet it now appears they were part of a wider network of terrorism and had been known to Special Branch and the security services prior to July 7, for some years in fact.

The Metropolitan Police declined to respond to claims by an unnamed senior security official who told The Sunday Times about the bug in Khan’s car. “We don’t discuss matters of surveillance or intelligence,” a spokesman said.

Martin Gilbertson, a computer expert who worked with some of the bombers near their homes in Leeds, claimed in The Guardian that he had alerted police to their threat two years before the attacks.

West Yorkshire Police said: “We do not discuss intelligence matters and therefore we can’t comment on specific actions.”

The book The One Percent Doctrine by the journalist Ron Suskind claimed that Khan was so dangerous he was banned from flying to America two years before the bombings.

The FBI said: “That reporting is inaccurate.” It suggested the author had confused Khan with Mohammed Ajmal Khan, who was jailed in Britain for nine years after buying weapons for Pakistani terrorists. Suskind denies mistaken identity.

UNANSWERED QUESTIONS

CLAIM

Investigators found a bug in Mohammad Sidique Khan’s car, proving that Special Branch had him under surveillance

— The Sunday Times

RESPONSE

“We don’t discuss surveillance or intelligence” — Scotland Yard

CLAIM

A computer expert working at the heart of Khan and Tanweer’s group of radical Muslims in Leeds tried to warn police but was ignored

— The Guardian

RESPONSE

“Cannot comment on terrorism” — West Yorkshire Police

CLAIM

Khan was banned from flying to America because he was viewed as a terror risk plotting to blow up synagogues on the East Coast

— Ron Suskind in his book, extract printed in The Times

RESPONSE

It was a different Khan, the FBI says. Suskind denies confusing the two men

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