David Cameron has defended a letter that urged mosques to combat radicalism in the wake of the terror attacks in France but was criticised for suggesting Islam is "apart from British society".
Cameron said Eric Pickles' letter, which told more than 1,000 Islamic leaders they "had more work to do" to root our extremists, was "reasonable, sensible and moderate".
He added: "Anyone, frankly, reading this letter, who has a problem with it, I think really has a problem."
This will not please The Muslim Council of Britain (MCB), which said the letter appeared to re-enforce claims by the far right about Islam's place in Britain.
MCB deputy secretary-general Harun Khan said: "We will be writing to Eric Pickles to ask that he clarifies his request to Muslims to 'explain and demonstrate how faith in Islam can be part of British identity'.
"Is Mr Pickles seriously suggesting, as do members of the far right, that Muslims and Islam are inherently apart from British society?"
Answering questions after a speech in Ipswich on Monday, Cameron said: "I think it is absolutely right to write this letter, to say that we all have a responsibility to fight extremism.
"Anyone who reads this letter - and I've read the letter - will see that what he is saying is that British Muslims make a great contribution to our country, that what is happening in terms of extremist terror has nothing to do with the true religion of Islam.
"It's being perverted by a minority who have been radicalised. But everyone needs to help with dealing with this problem of radicalisation."
He added: "I think it is the most reasonable, sensible, moderate letter that Eric could possibly have written.
"Frankly, all of us have a responsibility to try to confront this radicalisation and make sure that we stop young people being drawn into this poisonous fanatical death cult that a very small minority of people have created."
In the letter sent to more than 1,000 Islamic leaders, Mr Pickles and communities minister Lord Ahmad stressed that they were "proud" of the way Muslims in Britain had responded to the Paris terror attacks but added that there was "more work to do".
"You, as faith leaders, are in a unique position in our society. You have a precious opportunity, and an important responsibility, in explaining and demonstrating how faith in Islam can be part of British identity," they wrote.
"We believe together we have an opportunity to demonstrate the true nature of British Islam today.
"There is a need to lay out more clearly than ever before what being a British Muslim means today: proud of your faith and proud of your country. We know that acts of extremism are not representative of Islam, but we need to show what is."