British trade unions representing six million workers today urged their members to vote to stay in the European Union, warning that a Brexit would threaten workers' rights.
The general secretaries of Unite, Unison and the GMB were among 10 union leaders who wrote a letter to the Guardian newspaper claiming that parental leave and holiday rights would be under threat without EU protection.
"Maternity and paternity rights, equal treatment for full-time, part-time and agency workers and the right to paid leave - continue to underpin and protect working rights for British people," read the letter.
"If Britain leaves the EU, we are in no doubt these protections would be under great threat. The Tories would negotiate our exit and, we believe, would negotiate away our rights," it said.
Len McCluskey, boss of Unite - Britain's biggest union - has not always been a vocal supporter of the EU, and threatened to call for a vote to leave if Prime Minister David Cameron diluted worker rights when renegotiating Britain's EU membership.
Cameron is set to join left-wing adversaries including former Labour interim leader Harriet Harman and Green Party leader Natalie Bennett later Monday to push for a remain vote in the June 23 referendum.
Recent polls have shown the "Leave" camp closing the gap, but bookmakers still believe that the "Remain" camp is strong favourite.
