British Prime Minister David Cameron has teamed up with a senior trade unionist to warn the UK's workers face a "triple threat" to jobs, wages and the cost of living if the country votes to leave the European Union.
The prime minister and Sir Brendan Barber, former general secretary of the Trades Union Congress, have written a joint article in The Guardian to warn an Out vote on 23 June would leave the UK "a poorer country in every sense".
Putting aside their political differences in an unprecedented Tory-union double act, they highlighted a PwC analysis which suggests unemployment could rise to 8 per cent in the event of a "Brexit", compared to 5 per cent inside the union.
They also claimed that leaving Europe could put pressure on the pound, writing, "A weak pound means more expensive goods and higher inflation - pushing up the prices of the weekly shop, clothes, petrol - anything we import from other countries.
"So we are likely to see the cost of living going up, just as wages are being squeezed and jobs are being lost. That is the threat for families already struggling to make ends meet - and a risk working people and the poorest in our country simply cannot afford."
Cameron and Sir Brendan also claimed certain privileges guaranteed to workers by the EU, such as paid holidays, maternity rights and equal treatment for part-time workers could be plunged into jeopardy if the UK left.
The claims, which will be dismissed by the Leave campaign as more scaremongering, follow government concessions in the bitterly opposed Trade Union Bill.
During a debate in the Commons, Scottish National Party MP Tommy Shephard claimed the concessions could be an attempt to prevent a conflict with the trade unions so they would support the government's position of staying inside the EU.
And UKIP MEP Mike Hookem said, "The unions are supposed to be defenders of UK workers, not the ones selling them down the river in return for political favours."
In response to their Guardian column, a Vote Leave spokesman said: "Two members of the political establishment doing down the British economy is nothing to be proud of."
The latest row comes as Brexit campaigner and employment minister Priti Patel said an Out vote would allow the UK to "strip out" EU laws which affect small businesses - with claims Brussels red tape costs the country as much as £125 billion a year.