GAVIN Barwell MP is to seek an urgent meeting with Health Secretary Jeremy Hunt in hope of persuading NHS Croydon board members to answer questions about the trust's £28 million overspend.
The Croydon Central MP said it was "unprecedented" that public officials, including the former chief executive and chairman, have refused to appear before an inquiry tasked with investigating what went wrong.
His criticism comes as David Fitze, chairman of the primary care trust's audit committee at the time, became the latest figure to snub the South West London joint health and overview scrutiny committee.
Last week, the Advertiser revealed former chairman Toni Letts, now vice-chairman and a Labour councillor, had joined former chief executive Caroline Taylor in refusing to give evidence.
Mr Barwell said: "It's not acceptable for anyone who held a senior executive or non-executive post to refuse to cooperate with the investigation.
"In fact, it's unprecedented. I will be raising it with the Secretary of State as soon as possible."
The lack of co-operation from key figures at NHS Croydon threatens the credibility of the scrutiny committee, set up by Croydon, Sutton, Wandsworth, Kingston and Richmond councils.
Cllr Fitze, a councillor for Fairfield ward, refused to appear before the committee following an accusation levelled by his predecessor John Power that he lacked the qualifications to be chairman of an audit committee.
Council leader Mike Fisher, who led calls for the inquiry to be set up, said he would speak to Cllr Fitze to "express the need for openness and accountability".
He added: "David is extremely transparent and accountable. I will see whether he can be persuaded to give evidence.
"But accountability is essential across the board. Top of the list in terms of who should appear is the chairman and particularly the chief executive, who continues to work in the NHS."
Labour leader Tony Newman said he would not try to persuade Cllr Letts to give evidence because he believes committee chairman Jason Cummings has already "made up his mind".
Cllr Cummings, a councillor for Heathfield ward, told the Advertiser last week the panel had little choice but to conclude that anyone who refuses to give evidence has "something to hide".
"I won't try to persuade Toni because I share her grave concerns about Cllr Cummings's outrageous comments and that he appears to have pre-judged his conclusions," said Cllr Newman.
NHS Croydon posted a surplus of £5 million in 2010/11 when it had in fact overspent by at least £23 million.
The committee has been unable to locate former director of finance Stephen O'Brien, whose extended periods of sick leave left interim deputy finance director Mark Phillips effectively in control of the finances.
An independent report by Ernst & Young found Mr Phillips made "unwarranted adjustments" to the agreement of balances while working "largely unsupervised", but the panel has been unable to contact him either.
Cllr Newman said that the absence of evidence from either of these figures meant the committee could not reach valid conclusions.
He added: "Without their evidence I don't see what would be gained from hearing from Toni."
Cllr Newman, vice-chairman of NHS Croydon at the time, has been invited to give evidence but has not yet appeared before the committee.
He said: "If it transpired there was something I could add then I would not rule out appearing."The panel has held crisis talks behind close doors to work out what, if anything, it can do to encourage witnesses to give evidence. It has no power to compel people to attend and admits that a request for assistance sent to the Department of Health is likely to prove fruitless. Chairman Jason Cummings said: "We had a positive discussion in terms of where we are at and the options available to us. "We haven't given up hope of getting a couple more people to come along. "There are things going on behind the scenes to get these people to come and answer questions. "We have written to some of them with a list of questions to see if we can get some level of response. "Maybe they will be prepared to give a written response rather than risk appearing in person, in front of the media, where they might say something which puts them in a difficult position. "All we can do is push on and keep the pressure up." Internal auditors Deloitte and external auditors the Audit Commission, both of which missed the trust's financial irregularities, are due to give evidence before the committee next Monday (November 26). The panel hopes it will publish its findings and recommendations before Christmas.