LONDON (REUTERS) - Britain will not hold a second referendum on its membership of the European Union if the result of a June 23 vote is close, Prime Minister David Cameron said on Tuesday.

With just over five weeks to go until Britain's EU referendum, opinion polls are giving contradictory indications about the likely outcome of the referendum but some suggest the result will be on a knife-edge.

The leader of the anti-EU UK Independence Party, Nigel Farage, said in a newspaper interview published on Tuesday that if the result was as close as 52-48 per cent for "In", the debate would be "unfinished business".

"If the remain campaign win two-thirds to one-third that ends it," he told the Daily Mirror.

Asked by a reporter about the comments, Cameron said it showed the "Out" campaign was losing.

"I think when people start arguing for a second referendum before you've even had the first one, I think that clearly demonstrates that you are losing the argument," Cameron told an event hosted by the World Economic Forum.

"I am absolutely clear, a referendum is a referendum, it's a once in a generation, once in a lifetime opportunity and the result determines the outcome... You can't have neverendums, you have referendums."