A report that showed cutting vital services at St Helier would cost £100m more upfront than keeping it open was kept secret from a panel that recommended axing vital services at the hospital.
A councillor has claimed a decision as to which one of four hospitals’ should lose its maternity and A&E might have been different if the information was disclosed to the panel and been part of a fuller review.
As a recommendation to close the services at St Helier is due to be to formally recommended to an NHS board, a pressure group is calling for the review to be scrapped.
Earlier this year, a panel looking into non financial implications of shutting a hospital in south west London voted St Helier should lose its maternity and Accident and Emergency department as part of NHS south west London's Better Services Better Value (BSBV) review.
But results of a separate financial review carried out by finance experts and NHS financial directors were kept secret from the non financial panel.
BSBV said this was done at the request of councillors on a Joint Overview and Health Scrutiny Panel on the basis it would "ensure value for money didn’t become an excessive driver at the expense of quality".
But Merton councillor Suzanne Evans, who sits on the joint panel, said councillors had repeatedly questioned why the scoring was being done independently of the financials.
She said: "I wasn’t part of the scoring panel, but I suspect it would have changed the outcome because if you are talking about delivering less healthcare for more money it seems to be a ridiculous situation - why would anyone want to offer less healthcare at a greater cost?
"It could have affected their recommendation as finances have got to be a consideration."
In the financial review, closing St Helier was the most expensive put forward with a total upfront capital cost of £286.9m.
Keeping four hospitals, the least expensive option at £184.2m, was deemed the least favourable option.
A BSBV spokesman said closing services at St Helier and opening a planned care centre the taxpayer would save £19m per year compared to a net cost should there be no change.
He said: "The capital to achieve any necessary redevelopment on other hospital sites would come from a mixture of internally generated capital by the relevant trusts and external capital to be provided by the Department of Health or other sources - the latter capital would be subject to the relevant approval processes, as is usual in any NHS service change programme.
Geoff Martin, chairman of London Hospital Emergency, said: "The idea that the scoring panel could have made a decision without very basic financial information makes a mockery of the process.
"There is now an overwhelming case for BSBV to be stopped in its tracks on the basis that the whole thing has been so badly mishandled and for the government and ministers to step in and halt the process before we reach the consultation."
A three month public consultation into the plans is due to start on October 1.