Unison has become the latest union to officially back Remain ahead of the EU referendum, in a huge blow to Leave campaigners.
After overcoming "its doubts", the union will encourage its 1.3m members to back continued EU membership, after over 78 per cent of its branches wanted the union to take a stance and 95 per cent of these branches backed a Remain vote.
It comes after Unite, the UK's biggest union, announced that it will campaign for the UK to stay in the EU as "the best hope for workers".
The GMB union also announced earlier this year that it "was time to be positive about the benefits to our economy jobs and our environment".
"Europe isn’t perfect, but on balance staying in the EU has so much more to offer nurses, teaching assistants, town hall staff and other public servants than an uncertain future where the UK goes it alone," Unison general secretary Dave Prentis said.
"Without the laws that began life in Europe, most people at work in the UK would be getting a very rough deal. If the June vote is to leave the EU, it would then be up to the government which laws stayed and which laws went. Unscrupulous employers would have a field day.
"Unison may have had its doubts about Europe in the past, but now the chips are down and exit is a real possibility, public sector workers know that the services they deliver, and the public that relies on them, will be much better off in than out," he added.
The union announced earlier this year that it was launching a consultation of its branches to determine how the organisation should campaign in the referendum.