Leaders of some of Britain's biggest trade unions have urged their members to vote for the country to stay in the European Union in the 23 June referendum. In a joint open letter published in the Guardian, the bosses of 10 trade unions — including Unite, Unison, GMB and TSSA — said an exit from the EU would endanger the hard-won rights of British workers.

They said they "simply do not trust" the Tory government to preserve rights such as maternity and paternity leave, equal treatment for full-time, part-time and agency workers, and the right to paid leave, in the absence of EU legislation.

The warning comes as Prime Minister David Cameron and notable figures from the left prepare to unveil a dossier that accuses the Leave campaign of deceiving the British public on the economic consequences of a Brexit.

"It's time for the Leave campaign to outline their economic plan for Britain outside Europe," the jointly-signed document from Cameron, Labour's Harriet Harman, Lib Dem's Tim Farron and Greens' Natalie Bennett will say, according to Press Association.

"They are perpetuating an economic con-trick on the British people, and we're calling time on it. The British public deserve better than being asked to roll the dice." Opinion polls released over the weekend showed 43% support among UK adults for a Brexit, with support for the Remain campaign coming in at 40%.

Tory in-fighting

"After much debate and deliberation, we believe that the social and cultural benefits of remaining in the EU far outweigh any advantages of leaving," trade union leaders said in the joint letter. "Despite words to the contrary from figures like Iain Duncan Smith and Michael Gove, the Tories would negotiate our exit and, we believe, would negotiate away our rights.

"We simply do not trust this government if they are presented with an unrestricted, unchecked opportunity to attack our current working rights." The in-fighting in the Tory ranks has grown increasingly fractious as the referendum edges closer, with Cameron pointing to the economic dangers of a Brexit as reason enough to stay in the EU.

"Their argument is: 'Let's wreck the economy by leaving the single market in order to do it'. I'm going to make them pay for that," he told the Daily Mail on 4 June.

"The idea that the world just gives you great trade access is nonsense on stilts. Boris [Johnson] wants us to be like America, so you'd be subject to WTO (World Trade Organisation) tariffs on cars, clothes, shoes. "It's common sense: if you cut yourself off from your biggest market your economy will be poorer — and they know that."