This comes after the Royal Borough went to the High Court this week to seek a judicial review of the former Berkshire Primary Care Trust's decision to move the hospital's minor injuries unit, shut its rehabilitation unit and permanently close the midwife-led birthing unit.
However, Heatherwood and Wexham Park NHS Foun-dation Trust plans to build a new centre at the Ascot site for planned surgery to replace outdated buildings there.
Following the news that the Royal Borough planned to seek a judicial review, trust chief executive Philippa Slinger said: "It would be a shame if the planning of this was delayed by a lengthy legal process."
Dr William Tong, from Bracknell and Ascot Clinical Commissioning Group (CCG), went further, claiming "the legal process could put at risk the development of the new state-of-the-art surgical centre at Heatherwood Hospital which is critical for local patients". Dr Tong - clinical chairman of the CCG, one of the clinical commissioning groups that replaced the primary care trust in April - added: "Proceeding to legal challenge will entail substantial legal costs for the local NHS and Royal Borough of Windsor and Maidenhead Council, at a time when budgets for frontline services are stretched.
"We will be strongly defending these important changes for local people in the courts."
The minor injuries unit at Heatherwood is set to be replaced by an expanded service in a new 'urgent care centre' at Brants Bridge, Bracknell, and Dr Adrian Hayter, chairman of Windsor, Ascot and Maidenhead CCG warned: "This challenge would mean we are unable to expand urgent walk-in services for patients in Bracknell, Ascot and Windsor at a time when accident and emergency services are under increasing pressure."
The planned merger between the cash-strapped Heather-wood and Wexham Park Trust and Frimley Park Hospital NHS Foundation Trust would also be at risk, according to the latter's chief executive.
Andrew Morris said: "I am concerned that this puts important plans for changes in local services at risk at a time when we are in delicate negotiations over the merger with Heath-erwood and Wexham Park.
"This potentially risks securing the significant investment that is much needed in the local health service."
Ms Slinger has said that Heatherwood and Wexham Park would end up being bust if the merger with Frimley Park did not go ahead.
Spike Humphrey, from the Save Heatherwood Hospital campaign, said: "It's important to challenge the decision and the Save Heatherwood campaigners have been talking about it for a long time. It's good news the borough council will do it.
"It is a crying shame that public money is going to be used but the whole way the NHS is going; crazy money is being spent on things such as £750,000 on the consultation which I think was flawed.
"The CCGs have got their fingers in their ears but I hope they will enter serious discussions rather than going all the way to judicial review."
The Royal Borough is seeking a judicial review on the basis it feels the consultation process over the changes was flawed.
Cllr David Coppinger, cabinet member for health, said: "The process was flawed. We really feel they made the wrong decision for our residents."
The council and NHS presented their arguments to a High Court judge on Wednesday, who will decide in six-eight weeks if there is enough evidence to undertake a judicial review.