The pair were greeted outside court with chants of "freedom"

A jury decided speeches by Mr Griffin and party activist Mark Collett in 2004 had not incited racial hatred.

Home Secretary John Reid said he would consult ministers after Gordon Brown said current laws may need reviewing.

Lord Chancellor Lord Falconer said Muslims were offended and must be sure that the law would protect them.

But Lib Dem MP Evan Harris said tighter laws could create "extremist martyrs".

Mr Griffin, 46 and from Powys, had denied at a retrial two charges of using words or behaviour intended to stir up racial hatred .

Secret filming

Mr Collett, 26 and from Leicestershire, was cleared of four similar charges.

The pair were charged in 2005 in the wake of the secretly filmed BBC documentary The Secret Agent, which had been broadcast a year earlier.

RELIGIOUS AND RACE HATE LAW The new Racial and Religious Hatred Act has made it an offence to stir up hatred on religious grounds and amends the law on encouraging racial hatred. It applies to the display, publication, broadcast or distribution of words or behaviour that is likely to stir up religious or racial hatred. Under previous hate law, Christians and Muslims did not get protection because they were not considered to constitute a single ethnic block. Prosecutors must still prove a criminal intent behind the words, rather than simply "recklessness" as the government had originally proposed before the bill was debated. Analysis: Hatred prosecution Q&A: Religious hate laws

The Leeds Crown Court jury heard extracts from a speech Mr Griffin made in the Reservoir Tavern in Keighley, West Yorkshire, on 19 January 2004, in which he described Islam as a "wicked, vicious faith" and said Muslims were turning Britain into a "multi-racial hell hole".

Mr Collett addressed the audience by saying: "Let's show these ethnics the door in 2004."

A Home Office spokesman said Mr Reid would "think carefully and take time to study and reflect on this [court] judgement and its implications, including taking soundings from his ministerial colleagues".

But the minister believed the "poisonous politics of race" could be defeated only by argument, politics and community engagement, the spokesman added.

Legislation banning the use of threatening words to incite religious hatred was passed by Parliament earlier this year and is expected to come into force in 2007.

"Parliament has only recently discussed and decided on new laws in this area," the spokesman said.

"But obviously we want to make sure legislation is effective and even-handed."

Any preaching of religious or racial hatred will offend mainstream opinion in this country Chancellor Gordon Brown

In the wake of the BNP pair's acquittals, Chancellor Mr Brown said: "Any preaching of religious or racial hatred will offend mainstream opinion in this country.

"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."

Lord Falconer later told BBC Radio 4's Any Questions? that the government had to show young Muslims that Britain was not anti-Islamic.

"We should look at them in the light of what's happened here because what is being said to young Muslim people in this country is that we as a country are anti-Islam, and we have got to demonstrate without compromising freedom that we are not," he said.

He said there should be "consequences" from saying Islam is "wicked and evil".

Hatred law

Freedom of speech should not be an excuse for people to insult an entire community, Lord Falconer added.

But Dr Harris, who is on the influential joint select committee on human rights, said: "Although I am disappointed these members of a racist party were not successfully prosecuted for race hate given their attacks on Asians and asylum seekers, Parliament must resist the temptation for more restrictions on freedom of expression."

He added that extending restrictions "can be counter-productive by either creating extremist martyrs or being impossible to enforce".

Dr Harris argued there were "enough laws to deal with speech which actually incites to violence or other criminal offences, or which uses threatening language".

"There must be room in a free society to allow even offensive criticism of religions and their followers," he added.

After the not guilty verdicts, Mr Griffin said: "What has just happened shows Tony Blair and the government toadies at the BBC that they can take our taxes but they cannot take our hearts, they cannot take our tongues and they cannot take our freedom."

In a statement, the BBC said its job was to bring matters of public interest to general attention.