British Prime Minister David Cameron and ex-footballer David Beckham have made last-minute appeals to voters to back staying in the European Union, two days before a referendum.

Britain vote on Thursday on whether to quit the 28-nation bloc, amid warnings from world leaders, investors and companies that a decision to leave would diminish the former imperial power’s influence, unleash turmoil on markets and send shock waves around the Western world.

In a rare televised address outside his Downing Street office, Cameron repeated his message that leaving the EU would jeopardise Britain’s economy and its national security, with fewer jobs, fewer allies and higher prices.

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“Brits don’t quit,” he said, using the official backdrop to make a direct pitch to older voters considered more eurosceptic and more likely to vote.

“It will just be you in that polling booth. Just you, taking a decision that will affect your future, your children’s future, your grandchildren’s future.”

The Conservative prime minister’s intervention, which was billed as a significant statement but not publicised in advance, came as an opinion poll showed support for remaining in the EU shrinking.

The Survation poll put the “In” camp just one percentage point ahead of the campaign for a so-called Brexit, well within the margin of error.

Commentators said the hastily arranged appearance suggested Cameron, who promised the referendum in 2013 under pressure from MPs in his Conservative Party, and the “In” campaign were very worried about the outcome.

David Beckham weighed in on the conversation, urging people to vote to stay in the European Union.

The former Manchester United and Real Madrid player said the UK should be “facing the problems of the world together and not alone”.

Drawing on his playing days, he said the heart of Manchester United’s title winning teams in the 1990s would not have achieved so much without the input of players elsewhere in Europe.

“Now that team might have gone on to win trophies but we were a better and more successful team because of a Danish goalkeeper, Peter Schmeichel, the leadership of an Irishman Roy Keane and the skill of a Frenchman in Eric Cantona.”

He added: “I was also privileged to play and live in Madrid, Milan and Paris with teammates from all around Europe and the world.

“Those great European cities and their passionate fans welcomed me and my family and gave us the opportunity to enjoy their unique and inspiring cultures and people.

“For our children and their children we should be facing the problems of the world together and not alone. For these reasons I am voting to Remain.”

The EU – already shaken by differences over migration and the future of the euro zone – would lose its second-largest economy, one of its top two military powers and by far its richest financial centre.

Turnout is likely to be key to the result, and the ORB poll found that Remain supporters, who had been regarded as being more apathetic, were increasingly motivated to vote.