VIDEO & PICTURES: Labour deputy leader Tom Watson's 'Remain' campaign hits Wolverhampton

The bright red coach, emblazoned with the words 'Labour in for Britain', pulled up in Queen Square, Wolverhampton, as Mr Watson met supporters and spoke passionately about his desire to remain as part of the union.

Mr Watson, MP for West Bromwich East, said he plans to visit 20 cities over the next six weeks in the hope of convincing as many people as possible that Britain should stay in the EU before the crucial vote on June 23.

Labour's second-in-command said the country would be left facing an uncertain future if it did exit the EU and remaining in was vital for businesses in the Black Country.

He said: "We are the great manufacturing heartland of the UK and being in the EU opens up a market of 500 million people.

"It's pretty clear that supporting British manufacturing is about making it as easy as possible to get goods to market.

"It would leave us facing a very uncertain future. Businesses don't know how easy it will be to trade. It would be very difficult to renegotiate this agreement we have benefitted from and it might make it harder to trade in future."

Mr Watson, whose bus was also visiting Telford and Birmingham, placed a heavy focus on workers' rights and said many could be under threat in the event of a vote to leave.

He said: "This is where the Labour Party has got a unique message to give. Some our our hard-won protections in the workplace, treating part-time workers the same as full-time workers, maternity rights and many more will be under threat if we vote out."

A massive 80 per cent of people who took part in an Express & Star poll earlier this year said they wanted out of the EU but Mr Watson believes many have yet to make their minds up about which way they will vote.

"A lot of people are undecided," he said. That is why I am taking a personal leadership position within my own party. We have got to work hard to convince them, we have got to win their support on doorsteps, in schools and colleges."

The Labour leadership has been accused of not being clear enough on where it stands on the EU but Mr Watson said the top of the party was united on remaining. He also said criticism of leader Jeremy Corbyn over the issue was unfair.

He said: "I think it's very unfair on Jeremy. I have criss-crossed the country with him. He is speaking on the EU today. He did a speech in Liverpool on Sunday and he has more speeches to make in the coming months."