David Cameron warns of the dangers of Brexit

British Prime Minister David Cameron warned Sunday of the dangers of embracing "leave" campaigner Nigel Farage's vision of Britain ahead of the country's referendum on its European Union membership.

The UK Independence Party leader wants to take Britain "backwards" and divide rather than unite, Cameron said, as both sides in the referendum debate prepared to make a final push before the Thursday vote.

He made the argument in an article in the Sunday Telegraph as the battleground shifted to the news media with large rallies still on hold because of the Thursday slaying of Labour Party lawmaker Jo Cox.

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Former London Mayor Boris Johnson, a prominent "leave" campaigner from Cameron's Conservative Party, turned to the influential Sunday newspapers to press his case.

Johnson told the Sun on Sunday newspaper that a British exit, or Brexit, offers voters a "once in a lifetime" chance to change British life for the better. He said it would make a statement that would last through the ages.

Johnson had initially planned a major rally Sunday but it was cancelled after the Cox murder. Parliament has been recalled for a special session Monday to honour her memory.

It is not clear what impact, if any, the shocking killing of Cox will have on the vote.

A 52-year-old man has been charged with murder over the death of the lawmaker, who had publicly backed the "remain" side. When asked his name in court Saturday, the suspect said "death to traitors, freedom for Britain."

Some have criticized the tone of the Farage branch of the "leave" campaign for a poster unveiled hours before the shooting that used a photo of trudging migrants crossing Europe on foot that carried the capital-letter warning BREAKING POINT.

Treasury Chief George Osborne denounced the poster as "disgusting and vile" and called for a more civil debate in the aftermath of Cox's death. He accused the "leave" side of "making baseless assertions that millions of people are going to come into the country in the next couple of years from Turkey, saying that dead bodies are going to wash up on the beaches of Kent."

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Osborne compared the Farage poster to the Nazi propaganda of the 1930s.

Farage also returned to the public eye Sunday after a brief hiatus since the killing of Cox. He said on ITV that the "leave" campaign had probably lost some momentum because of the tragedy, which he blamed on "one person with serious mental issues."

"I don't know what's going to happen over the course of the next three or four days," he said as the campaign hangs in the balance.

Newspaper editorial boards also weighed in Sunday. The Sunday Times and Sunday Telegraph urged voters to leave the EU. The Observer and the Mail on Sunday endorsed staying within the bloc.

The Sun tabloid has earlier said it favors a Brexit.

Both sides are expected to resume full-scale campaigning shortly ahead of the Thursday vote.