The Government tonight suffered a major backbench rebellion which slashed its majority to just one in a vote on its controversial new anti-terrorism laws.

Voting was 300 to 299 as the Government came within a whisker of defeat on a rebel Labour amendment to the Terrorism Bill. It was the lowest majority for the Government in any vote in this Parliament and the last.

The amendment aimed to establish "intent" in the new offence of encouragement of terrorism, after cross-party complaints that the Government’s current definition was too widely drawn.

Earlier, the Government pledged a rethink on the measure as ministers tried to head off a damaging revolt. Home Office minister Hazel Blears said that she recognised "legitimate concerns" that a new offence of encouraging terrorism needed to be tightened up.

Her commitment to engage with critics was welcomed by John Denham, a former Labour Home Office minister, who suggested he would not now join a rebellion on this part of the Bill. But he warned her that if the talks did not result in changes to the proposals, she would face a further backlash.

In a later division the Government’s majority recovered to 16. Voting was 305 to 289, defeating a joint rebel Labour and Tory amendment which attacked moves to outlaw the glorification of terrorism.

The Government has been bracing itself for rebellion on its plans to create new terrorism offences. Last week 16 Labour rebels voted against the Bill’s second reading in a warning shot across the Government’s bows, and a high number of amendments have been tabled for today's debate.

MPs' concerns focus not only on the definition of encouraging and "glorifying" terrorism, but also on plans to allow the police to hold terrorist suspects for up to 90 days without charge. This issue is expected to be voted on later, during the Bill’s line by line committee stage.

Charles Clarke today accepted that proposals for the 90-day detention of suspects were "flexible", saying that although he was convinced that the police case to detain suspects without charge for 90 days - up from 14 days - was compelling, he was prepared to negotiate a consensus.

The Conservatives believe that the time-limit should be doubled to 28 days. The Liberal Democrats are arguing for retention of the 14-day limit with changes to allow police to press lesser charges to hold suspects while investigations continue.

Mr Clarke said that he was adopting a "conciliatory" approach but warned that the Government can not fight terrorism with "one legal hand tied behind our back".

He told the BBC: "I believe the 90-day case is made [but] I am ready to look for flexibility to achieve agreement as I believe the legislation is important.

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