Tony Blair has called for moderate Muslims to take on the extremist views held by some members of their communities.

Appearing before the Commons liaison committee, the prime minister said that "the government itself is not going to defeat this".

He was speaking as a survey for the Times found that 13 per cent of British Muslims considered the July 7 suicide bombers to be martyrs.

And Labour MP Sadiq Khan has said he is disappointed with the government's efforts to engage with the Muslim community.

"There has been limited progress but there is an air of despondency," he said.

Ahead of the first anniversary of the attacks on London, the Populus poll also found that seven per cent of Muslims believe that suicide attacks can be justified in some circumstances.

And 16 per cent feel that while the London attacks may have been wrong the cause was right.

However 56 per cent believe that the government is not doing enough to tackle extremism, more than the 49 per cent of the population as a whole which takes the same view.

Some 65 per cent also say their community needs to do more to integrate into society.

Quizzed on the findings, Blair said: "It is clear, as the poll also shows, that the overwhelming majority of Muslims utterly abhor this extremism and are completely opposed to the fanaticism that gives rise to it and are completely on the same side as everybody else in wanting to defeat it.

"The government has a role to play in this but, to be honest, but the government itself is not going to defeat this.

"If you want to defeat this extremism you have to defeat its ideas and, in particular, a completely false sense of grievance against the West and that has to be done by government, but also by mobilising the moderate majority of Muslims to go into the Muslim community and take these people head on."

Meanwhile Peter Clarke, head of the Metropolitan Police Force's anti-terrorist branch, has said that Britain's security forces are at full stretch with 70 ongoing investigations into potential threats.

Clarke said investigations had "intensified" during the last 12 months.

Meanwhile MI5 has revealed that al Qaeda sympathisers have been trying to join the agency as it seeks to recruit more people from ethnic minority communities.