A "gap in the law" needs to be looked at following the acquittal of the BNP's leader on a charge of inciting racial hatred, the attorney general has said.
Lord Goldsmith said the law was not what ministers had wanted
A jury last week said Nick Griffin had not broken race laws when he called Islam a "wicked, vicious faith".
New laws outlawing religious hatred were agreed by MPs earlier this year.
But Lord Goldsmith said he wanted to see if those new laws, watered down while they went through Parliament, were tough enough to "fill that gap".
Comments critical of religions could "stir up a great deal of hatred" against individuals, he told BBC Radio 4's Today programme.
Earlier this year, peers voted to put freedom of speech safeguards into the Racial and Religious Hatred Bill.
Under these, people can be convicted of inciting religious hatred only when "threatening" words and behaviour are used.
Ministers had wanted to include "critical", "abusive" or "insulting" words or behaviour, but were defeated.
These can be used to prosecute for inciting racial hatred but not religious hatred.
Sikhs and Jews already have full protection from incitement because they are regarded as distinct ethnic groups.
But Christians, Muslims and others do not have this.
Mr Griffin was acquitted of two charges of using words or behaviour intended to stir up racial hatred.
The case was brought under the existing laws. The new legislation on religious hatred had not yet come into force.
Lord Goldsmith said: "I think what it means is that it's absolutely right that we should be looking at that new law, but it's important to recognise that this wasn't the law that was being used in this prosecution.
"I think this prosecution shows that there is a gap in the law and we need to look to see whether the new law is going to fill that gap or not."
Chancellor Gordon Brown and Lord Chancellor Lord Falconer have already said the law may need to be looked at again.
Mr Griffin said his acquittal had been a victory for freedom. The jury at Leeds Crown Court had been "decent Yorkshire men and women" who had "seen common sense", he added.
Liberal Democrat MP Evan Harris, who led the opposition to the government's religious hate law proposals, said ministers had been "at pains" to show that "criticism, however strong, of religion - as opposed to religionists - would never be covered by their law".
The case involving Mr Griffin had been a "straightforward failure of prosecution under race hate laws".
Mr Harris added: "If any revision of the law is warranted - and I don't believe it is because of the cost to free speech and the risk of creating martyrs - then it is a broadening of race hate laws, not protection for religion, that is required."