NHS chiefs have snubbed MP Susan Kramer's request to hand over documents relating to the future of Kingston Hospital.
The MP for Richmond Park submitted a request under the Freedom Of Information Act for 'all correspondence, from August 31, 2009, onwards, discussing, analysing or referencing the future of maternity, A&E and any other services threatened with closure at Kingston Hospital'.
But officials blocked the request, saying it would take too much time and cost too much money.
Under national guidelines, Freedom Of Information (FOI) requests should take no longer than 18 hours and £450 per investigation.
A Healthcare for South West London spokeswoman said Ms Kramer's request far exceed this, adding: "We would be happy to consider a more specific request that can be handled within the 18 hour limit, which is set to safeguard public money from unduly expensive FOIs."
The request follows a pre-emptive campaign from Liberal Democrats Ms Kramer and the Kingston and Surbiton MP Edward Davey, who say they have had conversations with senior members of NHS staff about the risk to maternity and A&E services at Kingston Hospital.
According to leaked pages of the South West London Strategic Plan, health bosses are considering cutting the services at one of the four hospitals in the area.
Healthcare for South West London have so far denied any decisions have been made but have also refused to publish the plan, saying it is an internal document. They say they will go public with proposals in the summer but have warned "no change is not an option".
Ms Kramer said it was in the public interest for the documents to be released.
She said: "This answer just reveals the sheer volume of discussions that have been had about the future of our local NHS services, and further strengthens our case to get everything into the public domain. We have had a huge response to the campaign from local residents who want our local health services to be protected. They are outraged that the plans have been kept secret from them for so long.
"I will keep on putting pressure on the government and the NHS to release the full details of their plans. If the government thinks it can continue to work on these proposals without having to answer to the local community then they are very much mistaken."