The £220m re-development of St Helier hospital has been put at risk by the collapse of plans to merge with a neighbouring hospital, an MP has said.

Siobhain McDonagh said yesterday's announcement that St George's in Tooting would not merge with the Sutton centre had been sparked by GPs predicting less demand for St Helier's services in the future.

The MP for Mitcham and Morden attacked GPs taking part in a review of health services in south west London, warning their views had put plans for 346 new beds and a multi-million pound refurbishment at the St Helier site doubt.

She said: "The money is there but will the Government spend it if there isn't a viable hospital?"

Bosses at St Helier, currently merged with Epsom Hospital, were pursuing a new merger with St George's in a bid to achieve foundation trust status - which would give the hospital more independence and financial freedom.

But, at the same time, doctors and other clinicians at NHS South West London have been running the Better Services Better Value review, examining how healthcare might be provided in the years ahead. GPs are set to take control of local health spending as part of nationwide NHS shake-up.

Ms McDonagh said: "The left hand doesn't know what the right hand is doing."

She said GPs were overstating the amount that services based at St Helier would be moved to other locations and providers in the future. She said she would meet health bosses later this week, and try to raise questions about the hospital's fate in parliament.

Ms McDonagh said uncertainty about the Government's health reforms had triggered the hospital's problems - but there was not time to wait for a clearer national picture before taking action to help St Helier.

She said: "The light of reason and reality needs to be shone on this... We have to get a result now. I don't think the game's over."

Matthew Hopkins, Trust Chief Executive, said: “We remain absolutely committed to the £219 million redevelopment of St Helier Hospital, which we know will bring enormous benefits to our patients, local people and staff.

“The Government have been very clear that this money is set aside for us to spend. The redevelopment of St Helier is long overdue and marks the single biggest investment in healthcare in the local area for a generation.

“We have already spent more than £5 million on the project and look forward to beginning the move of services and staff from the areas that are due to be demolished, prior to the work taking place. This phase, and the eventual demolition, will cost over £12 million and are due to be approved by the Department of Health by the end of February 2012.

“Crucially, the redevelopment continues to receive the highest level of support from our partners, including our strategic health authority NHS London, local GPs, MPs, councils, other local NHS partners, and – fundamentally – our staff, patients and local people.”