David Cameron has rejected claims an EU referendum will damage the UK economy, criticising those who argue the UK should stay in the EU come what may.
The prime minister told the CBI conference the UK was securing more inward investment than the whole of the EU despite his 2017 referendum pledge.
He also said he would toughen migration controls, despite business concerns.
At the same event Labours Ed Miliband said it was dead wrong to think the UK would be better off outside the EU.
Meanwhile, Deputy Prime Minister Nick Clegg warned that the UK would have no future outside the European Union.
With a general election six months away, the three leaders of the largest Westminster parties have been seeking to reassure business leaders that their views on an EU referendum are in the UKs national and economic interest.
Businesses have warned that the prospect of a referendum is causing uncertainty and could deter them from looking to expand or hire new workers.Extraordinary investment
But Mr Cameron rejected claims that a referendum would destabilise the economic recovery, suggesting there were months when the UK was securing more inward investment than the whole of the EU combined despite the warnings about its future membership.
If there has been uncertainty, why is it that there has been such an extraordinary period of investment into our country? he asked the conference.