MP Tony Baldry has asked county health bosses to come clean over cuts to mental health services in Banbury.
He wants to know if cuts are being made because of financial pressures and not, as claimed, because of restructuring.
Mr Baldry has written to Julie Waldron, manager of the Oxfordshire Mental Health Care Trust, saying the trust's consultation process was losing credibility by not spelling out the real reason for cuts.
The letter follows a public meeting in Banbury two weeks ago at which Mr Baldry and mental health charity MIND launched a "Save our Services" campaign.
Mr Baldry said: "The continuing cuts in mental health care are making people worried about future treatment. There is no support in north Oxfordshire for closing the Fiennes Older People Day Care Centre at the Horton Hospital. If the Fiennes Unit is closed, local belief is that it will not be replaced by something as good. In terms of integrity and confidence, the trust might have greater credibility if it distinguished more clearly between changes which it believed were in the interests of patients and those which are the result of funding cuts."
Mr Baldry thought mental health services locally were under funded. He said: "I understand that the Thames Valley Strategic Health Authority received 21 per cent less for health care than the English average, which obviously means there is 21 per cent less money to spend.
"I also understand that the Thames Valley Strategic Health Authority receives £125m less than the next worst-funded strategic health authority in the country. If we cannot sort out this disparity in funding, the problems faced by the NHS in Oxfordshire are simply going to recur each year and get more difficult each year."
Oxfordshire Mental Healthcare Trust has formally merged with its neighbouring organisation to become Oxfordshire & Buckinghamshire Mental Health Partnership NHS Trust.
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