David Cameron has said he is “deadly serious” about securing EU reforms and said that if his renegotiations failed “we will have to ask ourselves – ‘is this organisation for us?’”.
The prime minister told the CBI conference the issue was not whether the UK could survive outside the EU but whether it would be more successful.
He added that “the status quo isn’t good enough for Britain”.
The PM is to set out his reform proposals in detail on Tuesday (today).
David Cameron has said the UK needs to negotiate a “better deal” from its membership of the EU and will hold an in-out referendum on the issue by the end of 2017 – although he has not said when the vote will be hold.