"Free speech is a necessary condition for scientific debate and is the best way to rational conclusions about what the truth is," Mr Sigfrid, a Moderate Party MP, told the Herald.

"It's a very dangerous thing to replace open debate with violence from the Government when someone opposes what the conventional truth is."

He pointed out that the EU required entrant applicants, such as Turkey, to ensure freedom of speech and did not think existing members of the EU should be able to restrict free speech in such a way.

"It seems like a huge step backwards," Mr Sigfrid added.

He wanted EU citizens to be able to travel freely to countries like Ireland and not have to face the threat of legal action for freedom of speech which was accepted in Sweden and other countries, he said.

Under the law, an EU citizen could be punished for making a comment that is found to be offensive to a substantial number of followers of a religion.

The new Defamation Law renews the offence of blasphemy provided for under 1960s legislation with a punishment of a €25,000 fine.

It is due to be enacted in October, and groups such as Atheist Ireland have vowed to campaign against Justice Minister Dermot Ahern signing it into law.

mlavery@herald.ie