Jonathan Ashworth, the shadow secretary for health and social care, said a rescue package for the department would be a "day one priority" for a Labour government.
He was speaking after a tour of the hospital's A&E and women's and children's centre, in which he spoke to doctors and bosses.
Mr Ashworth said: "It is clear to me that when you have a town the size of Telford, growing quickly and attracting investment, the town needs an A&E.
"I visited here about a year ago and the future of the A&E department was a concern then.
"We're very concerned about the future of the department, we do not want to see an overnight closure.
"As the health secretary I would immediately put in place a rescue package for the hospital."
He said Labour would seek to increase investment in the NHS generally, and that money raised would come from higher taxes on high earners.
The leader of Telford & Wrekin Council, Shaun Davies, and Labour's prospective parliamentary candidate for Telford, Katrina Gilman also attended the tour.
Mr Davies said that he felt the opposition that has been registered to the overnight closure, through a petition and a march last weekend, should mean the end of the plans.
He said: "If I was a betting man, I think the amount of political and community opposition should make it politically impossible to close the A&E overnight."
But he stressed that even if the "battle" over overnight closure is won, the council will continue to fight the "war" against any possible overall downgrading of the service.
The council's online petition has reached more than 32,000 signatures, while Sunday's march through Wellington drew thousands of people protesting the closure.
While touring the A&E department the politicians spoke with consultant Ed Rysdale, who said the Wellington march was a sign of communities standing behind hospital staff.
He said: "It was a positive thing for us.
"The community support shows how much we are valued by people."
Ms Gilman paid tribute to the staff at the hospital, saying: "You provide first class care in often second class conditions."
Dr Adam Gornall, the hospital trust's clinical director for maternity, presented some of the trust's recent improvements.
He demonstrated the trust's maternity figures for perineal trauma during pregnancy, emergency caesarean section deliveries and neck injuries to babies, all of which are far below the national average.
On his impressions of the hospital, Mr Ashworth said: "I go to visit a lot of hospitals and you can sense the atmosphere when you walk around.
"Here there is a nice atmosphere and a really nice buzz around the staff."