Abu Hamza was convicted of inciting murder and racial hatred

He urged MPs to back ministers' plans to introduce an offence of "glorifying" terror in a vote next week.

Mr Clarke said the authorities had lacked the "confidence" to prosecute radical cleric Abu Hamza al-Masri until the government had tightened up laws.

Conservatives had to help further "strengthen" legislation, he added.

Abu Hamza, 47, from London, was jailed on Tuesday for seven years for inciting murder and racial hatred.

Prosecutors said there had been insufficient evidence to charge him before 2004.

'Strengthening law'

The preacher was, however, well known to the authorities for years before his arrest.

But Mr Clarke told BBC Radio 4's Today programme: "Both the police and the CPS did not have confidence of getting convictions in the courts."

He added: "We have to continue strengthening the law as we have done."

Some people did not want to believe how serious it all was David Blunkett, former home secretary Blunkett hits out Send us your views

Mr Clarke said there had to be a system-wide "determination to secure convictions".

Last month, peers voted to drop plans to create an offence of "glorifying" terrorism, claiming it would be "confusing" and unworkable.

Ministers have vowed to overturn the defeat when the Terrorism Bill returns to the Commons next Wednesday.

Meanwhile, former home secretary David Blunkett has said lawyers, security services and police were "deeply reluctant" to act against Abu Hamza before 2004.

He wrote in his Sun newspaper column: "Some people did not want to believe how serious it all was."

The CPS confirmed that it twice received files on Abu Hamza before 2004.

Officials concluded on both occasions "there was clearly insufficient evidence for a prosecution".