Tory MP Douglas Carswell revealed he had not told David Cameron he was defecting to Ukip.
Carswell "I've not yet spoken to the Prime Minister...if I'd phoned him up beforehand you'd have heard about it in another way"
The Prime Minister and Mr Carswell's relationship has not always been friendly, with Mr Cameron once telling the Clacton MP he needed to "get a sense of humour".
ITV News Political Correspondent Paul Brand is following updates from the special Ukip press conference at which Mr Carswell is speaking.
Carswell says he thinks members of his local party will come with him. But feels sad to be leaving them.
More top news
Theresa May will hold fresh talks with European Council president Donald Tusk during a summit in Brussels today.
Ireland is facing the prospect of a winter general election after rival parties called on the Tanaiste to quit.
An investigation has estimated there are tens of thousands of predatory accounts, with paedophiles evading protection mechanisms.