Labour leader Jeremy Corbyn will plead with the whole of the British Labour movement to get behind the Remain campaign, with just nine days to go before the EU referendum on 23 June. The left-winger will appear alongside his shadow cabinet colleagues at Trades Union Congress (TUC) House in central London to make the pro-EU speech on 14 June.
"Today sees my shadow cabinet and the trade union movement join together, in the interests of the people of this country, to make Labour's case to remain in the European Union and bring reform to strengthen workers' rights," he will say.
"That's why today I am issuing a call to the whole Labour movement, to persuade people to back Remain to protect jobs and rights at work. We have just nine days to go to convince Labour supporters to vote Remain."
The comments will come after former Labour Prime Minister Gordon Brown relaunched the party's Labour In for Britain campaign, which is chaired by former Home Secretary Alan Johnson.
Pro-EU prime minister and Conservative leader David Cameron had been taking a leading role in the Remain campaign, but Labour voters are likely to prove vital in the close race.
A vast majority of Labour MP and the UK's largest trade unions, including Unite and Unison, are also backing Remain at the historic ballot. However, rails unions the RMT and Aslef are supporting a Leave vote, while some Labour MPs, such as Vote Leave's Gisela Stuart, are campaigning for a Brexit.
Klevin Hopkins, the Labour MP for Luton North, has claimed a Leave vote would save the NHS from the controversial Transatlantic Trade and Investment Partnership (TTIP) agreement between the EU and US.
"We need to take back control of our public services, and strike trade deals on our own terms," he wrote for IBTimes UK.
"These deals should be conducted by democratically elected politicians in the full light of day, and they should put the interests of working people above those of companies. The EU is defending the interests of big business and not working people."
The latest opinion from YouGov for The Times, of more than 1,900 people between 12 and 13 June, put Leave on a seven point lead over Remain (46% versus 39%), with 11% of respondents undecided.