Prime Minister David Cameron warned voters Tuesday against believing "untruths" peddled by the Brexit campaign, seeking to regain momentum in the referendum race ahead of a crucial TV grilling.

As hundreds of thousands of people rushed to register for the June 23 referendum ahead of a midnight deadline, Cameron urged the public: "Don't make this choice on the basis of false information."

Opinion polls on Monday gave the campaign for Britain to leave the European Union a slender lead, sending the pound temporarily tumbling as concerns grow over the global market turmoil that could follow a Brexit.

The polls increased pressure on Cameron ahead of a television grilling by a live studio audience at 2000 GMT, when he will appear alongside -- but not debate -- UK Independence Party (UKIP) leader Nigel Farage.

In a hastily-arranged press conference ahead of the ITV (LSE: ITV.L - news) show, Cameron said: "It (Other OTC: ITGL - news) 's time the 'Leave' campaign was called out on the nonsense they are peddling."

He rejected claims that non-eurozone Britain could be forced to contribute to future eurozone bailouts, that its EU budget rebate was at risk, or that the economic benefits of leaving outweighed the potential costs.

Meanwhile WTO Director General Roberto Azevedo warned that British exporters could face an extra £5.6 billion ($8.2 billion, 7.2 billion euros) of annual customs duties if Britain left the EU.

His comments follow other warnings by the IMF and the governor of the Bank of England about the economic risks.

"Listen to the experts, don't stand on the sidelines -- this matters for you," Cameron urged voters.

He accused his rivals of "resorting to total untruths to con people into taking a leap in the dark. It is irresponsible. It is wrong."

- 'Blind panic' -

"Leave" moved into the lead in the WhatUKThinks polling average on Monday for the first time in weeks, with 51 percent against 49 percent for "Remain", excluding undecided voters.

The latest polls on Tuesday put "Remain" back in the lead with 51 percent to 49 percent, but this is uncomfortably close for Cameron with just over two weeks to go.

In a potential boost to his campaign, figures from the Electoral Commission revealed a sharp rise in the number of young people registering to vote in the referendum.

Some 226,000 people applied on Monday alone, including 148,200 people under the age of 34 -- a group which is overwhelmingly in favour of staying in the EU.

But Vote Leave accused Cameron of making his latest remarks out of "blind panic".

Lead campaigners Boris Johnson, the former London mayor and tipped as a future premier, and Justice Secretary Michael Gove challenged Cameron to a head-to-head debate to establish the facts.

The public "deserve the chance to hear these issues debated face-to-face between the prime minister and a spokesman for Vote Leave so they can judge for themselves which is the safer choice," they said in a joint statement.

- 'Legitimising racism' -

Cameron was criticised in the press for his performance in a TV event last week, and he will be hoping for a better reaction from the programme with Farage.

The UKIP leader is not part of the official Vote Leave campaign but has been dictating the Brexit agenda with his relentless focus on cutting back on the hundreds of thousands of EU migrants who come to Britain each year.

In a new video, the "Remain" camp highlighted derisory comments Farage has made about gay people, Romanian migrants and ethnic minorities.

"Share (LSE: SHRE.L - news) this video if you don't want to live in Farage's Britain," it said.

Archbishop of Canterbury Justin Welby also attacked Farage after he suggested women in Britain may be at risk of mass sex attacks by migrants.

"That is giving legitimisation to racism," Welby told a committee of MPs.

But Vote Leave maintained the focus on immigration by publishing details of 50 EU citizens convicted of serious crimes in Britain who cannot be deported because of the bloc's laws and court rulings.

"This puts British families at risk," said junior justice minister Dominic Raab.

Junior immigration minister James Brokenshire, for the "Remain" camp, countered that the European Arrest Warrant had allowed the deportation of 6,500 criminals since 2010.

Source: AFP