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," AFP reports.

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.