Muslim preacher Anjem Choudary has branded Christmas "evil" in a sermon posted on the internet.
The lawyer, who recently praised the Mumbai terror attacks, urged all Muslims to reject traditional Christmas celebrations, claiming that they are forbidden by Allah.
The 41-year-old shocked Christians and even those of his own faith by branding yuletide festivities as "the pathway to hellfire".
Choudary, who is chairman of the Society of Muslim Lawyers, ruled out all celebrations, including having a Christmas tree, decorating the house or eating turkey.
In the sermon posted on an Islamic website, he said: "In the world today many Muslims, especially those residing in western countries, are exposed to the evil celebration Christmas.
"Many take part in the festival celebrations by having Christmas turkey dinners.
"Decorating the house, purchasing Christmas trees or having Christmas turkey meals are completely prohibited by Allah.
"Many still practise this corrupt celebration as a remembrance of the birth of Jesus.
"How can a Muslim possibly approve or participate in such a practice that bases itself on the notion Allah has an offspring?
"The very concept of Christmas contradicts and conflicts with the foundation of Islam.
"Every Muslim has a responsibility to protect his family from the misguidance of Christmas, because its observance will lead to hellfire. Protect your Paradise from being taken away – protect yourself and your family from Christmas."
Choudary is Principal Lecturer at the London School of Shari'ah and a follower of the Islamist militant leader Omar Bakri Mohammed.
Earlier this year, he led a meeting at the heart of the area where the liquid bombers lived, which warned of a British September 11.
Well, he's a perfect example of the opposite of what Liberal Democrats believe in, isn't he? If so, it would be good to see a bit more condemnation from the Lib Dems of this sort of thing.
All I can say is, it's good to see that many Muslim families are apparently having turkey dinners - that's their choice, they should be free to do it.
We have to make sure that Mr Choudary continues to lose the argument- and isn't allowed to win through fear and intimidation.