Another leading union has decided to support the campaign for the UK to remain in the European Union.
Delegates at the annual conference of the shopworkers' union Usdaw voted to back the In campaign following a similar decision on Monday by the Communication Workers Union.
Usdaw leader John Hannett told the Blackpool meeting: "We simply cannot hope to be better off through going it alone. To be able to prosper, we need a growing economy that protects employment rights and the best way to grow our economy is to ensure we can trade with, influence and benefit from being in one of the world's largest trading blocks.
"Through the Social Europe project, we have been able to agree a minimum floor of terms and conditions. The core EU employment rights that Usdaw members rely on. Rights such as paid holiday leave, protection against discrimination, equal treatment for part-time workers, protection for transferring workers and improvements in holiday pay.
"If we were to leave the EU, there is a clear risk that such employment rights and protections would be dismantled by a UK Conservative Government.
Worker's rights, jobs and our place in the world are just three of the many reasons why we should be voting to remain in the European Union."
Alan Johnson, leader of the Labour IN campaign, told the conference that almost four million trade unionists were opposed to Brexit.