The Home Secretary has said comments by Ukip leader Nigel Farage about the Charlie Hebdo attack in Paris were "irresponsible."
Mr Farage said the attack was the result of "having a fifth column" living in Western countries opposed to their ideals.
He told Channel 4 News:
There is a very strong argument that says that what happened in Paris today is a result - and we've seen it in London too - is a result I'm afraid of now having a fifth column living within these countries.
We've got people living in these countries, holding our passports, who hate us.
Luckily their numbers are very, very small but it does make one question the whole really gross attempt at encouraged division within society that we have had in the past few decades in the name of multiculturalism.
Theresa May said it was "irresponsible to talk about a fifth column."
When asked about Ukip leader's comments, David Cameron said: "Today is not the day to make political remarks or arguments.
"Today is the day to stand four-square behind the French people."
Nigel Farage has told ITV News he expects to see "some cosmetic concessions" from German Chancellor Angela Merkel when she meets the Prime Minister later today.
However, the Ukip leader stressed Merkel "will not budge" on the principle of freedom of movement in the European Union.
"What I expect to see are some cosmetic concessions, perhaps the Germans agreeing that maybe child benefit should not be paid to children living in other parts of Europe," Farage said.
"But even if Mr Cameron later on today stands on the steps of Downing Street and says, 'This is a great victory' it still won't work, because the Poles have made it clear they will veto it anyway."
UKIP leader Nigel Farage has been criticised after his attempts to defend a former UKIP parliamentary candidate's remarks about Chinese people and homosexuals only appeared to make matters worse.
Mr Farage said controversial comments made by disgraced former Ukip candidate Kerry Smith were because he was a "rough diamond".
ITV News' Political Correspondent Carl Dinnen reports on how the controversy is affecting Mr Farage's popularity.
Nigel Farage has suggested a former Ukip candidate used the terms "chinky" and "poofters" because of his "council estate background".Read the full story ›
Nigel Farage has hit back at Russell Brand, saying the comedian and activist was "lighter weight than expected" and has a "personal make-up artist to straighten his chest hair".
Everyone fancied that Mr Brand and I might butt heads, but actually, as we entered the studio, and his personal make-up artist straightened his chest hair for him, I kid you not, I realised that perhaps he might be a bit lighter weight than expected.
For all Mr Brand’s posturing, he was really quite limp. Maybe it was the chapstick that his make-up artist applied to his lips at the last moment, but he didn’t seem to utter a word of sense.
The Ukip leader made the comments in a column for the Independent after the two appeared on BBC Question time last night.
Brand said 'we have to watch him' as he compared Farage to the Conservative politician best known for his 1968 "rivers of blood" speech.Read the full story ›
Leaders Live: Labour leader Ed Miliband has pledged to lower the voting age to 16 if he is PM after next year's General Election.Read the full story ›
Nigel Farage has told ITV Wales his comments on breastfeeding mothers were "wildly misrepresented".
The Ukip leader stressed that he was not against breastfeeding, but that he respects the rights of private businesses towards their customers.
Farage's suggestion that breastfeeding mothers should "perhaps sit in the corner" was met with widespread criticism yesterday.
Shadow Home Secretary Yvette Cooper has hit out at Nigel Farage after the Ukip leader said breastfeeding mothers should "perhaps sit in the corner" to avoid disturbing people around them.
Ms Cooper tweeted:
After *that* interview Nigel Farage should sit in a corner!
Ukip has insisted Nigel Farage "misspoke" after he appeared to disown the party's policy of banning sex education in primary schools.Read the full story ›