Britons face a "triple threat" to jobs, wages and prices in shops if the country votes to leave the European Union, David Cameron and former trade union leader Sir Brendan Barber have warned.

The prime minister and the former TUC general secretary warned that Brexit would leave the UK "a poorer country in every sense".

The pair acknowledged they were unlikely allies but the "special circumstances" of the EU referendum meant the "rules of conventional politics" could be temporarily set aside.

In a joint article in The Guardian, they highlighted analysis by accountancy giant PwC which suggested unemployment could rise to 8% if there was a Brexit, compared to 5% if the country stays in the EU.

Even if people kept their jobs "their wages will be lower than they would otherwise have been" because of the damage to productivity, while workers' rights would also be jeopardised.

They wrote that "while the two of us may disagree about quite how far this process should go, being in Europe has helped to deliver many of the crucial rights that underpin fairness at work".

Brexit would also weaken the pound meaning "more expensive goods and higher inflation", they said.

Vote Leave condemned the article by Mr Cameron and Sir Brendan. A spokesman said: "Two members of the political establishment doing down the British economy is nothing to be proud of."

Pro-Brexit Employment Minister Priti Patel will use a speech in the City of London to promise cuts to red tape if the country votes to leave.

"We could confine to history the bureaucratic excesses of Brussels," she will say.