A £220m redevelopment of St Helier Hospital has finally been approved by the Treasury, but the long-term future of accident and emergency and maternity services at the site remain in doubt.

Health Minister Mike O’Brien announced on Monday approval of the outline business case for the investment, which includes the demolition of the hospital’s aging five-storey Ferguson House.

But in an exclusive interview with the Sutton Guardian, he gave no guarantee the hospital would survive any closure or degrading of key services outlined in a controversial review by NHS London.

Healthcare for South West London has been looking at services at St Helier in Carshalton, St George’s in Tooting, Croydon’s Mayday and Kingston Hospital since June.

The review, which concluded only three of four hospitals in south-west London should have a maternity unit or an A&E, has cast doubt on the future of A&E and maternity services at St Helier.

Mr O’Brien said: “The £219m is an investment decision, but I can’t guarantee what the Treasury [regarding the review] will do. In realistic terms you can never predict what the next Government will do.

“At the moment there is no plan for closure of accident and emergency and maternity units.

“There will of course be financial restraints in the future, but this decision would not have happened without the constant lobbying from local MPs.”

Sutton and Cheam MP Paul Burstow said the investment gave St Helier a certain amount of security, but that campaigners had to remain vigilant.

He said: “This investment gives St Helier something it didn’t have before.

"If we had not got this ministerial announcement before the election I think the fate of St Helier would have been sealed and it would have become more of a satellite to St George’s.

"But we have to maintain our vigilance and make sure this new patient wing comes off the ground.”

At the announcement, Mr O’Brien said his arm had been “twisted” by “constant badgering” from Mitcham and Morden MP Siobhain McDonagh, Sutton and Cheam MP Mr Burstow and Wallington and Carshalton MP Tom Brake.

Mr Brake said: "This is the best local news we have had for decades.

"This investment will secure the future of St Helier Hospital and health services in the Borough for years to come.

"It is great news for patients, hospital staff and local businesses. I congratulate everyone involved in making this project happened."

The trust will develop the full business case, which, once agreed, means building would start in 2012, with a potential opening date of 2017.