Gordon Brown swiftly pledged to bring in tougher powers to raise the chance of convictions in similar cases, calling the BNP’s statements offensive.

His intervention came after an all-white jury decided that Nick Griffin, the BNP chairman, broke no law when he condemned Islam as “a wicked, vicious faith” at a secretly filmed meeting.

Plans for an offence of incitement to religious hatred were thrown out in a rare Commons defeat for the Government in February after a campaign led by the comedian Rowan Atkinson.

A watered down version was passed requiring that prosecutors prove intent and protecting freedom of expression but has yet to become law. It is expected to take force from February next year.

Although his speech focused on the alleged evils of Islam and was supportive of Sikhs, Mr Griffin, 47, could only be charged — alongside Mark Collett, 26, the BNP’s publicity director — with inciting racial hatred. It was their second trial, after a jury failed to reach a verdict at the first.

Mr Brown told BBC News 24: “I think any preaching of religious or racial hatred will offend mainstream opinion in this country and I think we have got to do whatever we can to root it out from whatever quarter it comes. And if that means we have got to look at the laws again, we will have to do so.”

Treasury sources indicated that John Reid, the Home Secretary, was thinking on similar lines.

Lord Falconer of Thoroton, QC, the Lord Chancellor, last night supported Mr Brown’s calls forreform of religious hatred laws. “We should look at them in the light of what has happened because what is being said to young Muslim people of this country is that we as a country are anti-Islam and we have got to demonstrate without compromising freedom that we are not.”

Sources close to the case claimed that it was politically-motivated and doomed to fail. The decision to prosecute was announced a day after Labour called last year’s general election.

The Times understands that West Yorkshire Police had concerns the trial represented a no-lose opportunity for the BNP. It was feared that Mr Griffin and Mr Collett would be portrayed as martyrs for free speech if they were convicted, while an acquittal would be greeted by the party as a huge publicity coup.

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