David Blunkett, Labour's health spokesman, said he would be writing to Virginia Bottomley, Secretary of State for Health, to ask precisely what information her department and the NHS management executive collect to monitor the changes. Several parliamentary questions have received the reply that the information was not collected centrally.
While health service academics have complained that information on how the system is working cannot be obtained, the Department of Health has launched a review by Touche Ross, the management consultancy firm, aimed at cutting out information currently collected that is 'unnecessary for the management of the NHS'.
Parliamentary questions have included how many GP budget- holders have been given extra cash because of likely overspends, what proportion of referrals outside normal contracts were refused by health authorities and the proportion of patients seen within 30 minutes of their appointment - a target under the Patient's Charter.
In some cases, ministers have suggested that Mr Blunkett contact health authorities direct. But Labour Party researchers say that in an increasingly secretive NHS, authorities show a growing reluctance to answer questionnaires.
A request last week for information on waiting times that the department is known to have collected has brought figures from some, but the North East Thames Regional Authority told its districts not to co-operate. The region said it wanted to check the districts' information and 'did not envisage' keeping it secret. But no guarantee was provided that the figures would be released.
Mr Blunkett's complaints brought a defiant response from Tom Sackville, a junior health minister, who said ministers tried to be helpful to MPs 'and are mindful of our need to be accountable. But we are not going to waste money that would otherwise be spent on patient care, feeding spurious campaigns by other politicians and campaign groups'.
But Klim McPherson, Professor of Public Health Epidemiology at the London School of Hygiene and Tropical Medicine, and a spokesman for the newly-formed health statistics users' group, said: 'There is an issue here that must be taken up in Parliament.'
Figures on how the system was performing were hard to obtain, he said, and written answers were a key source. 'This massive reorganisation may be working wonderfully well or it may be awful, but we will never know while we are denied the information on which to make a judgement.'
Mr Blunkett said he would be demanding that the Touche Ross study - whose existence was never announced, and only disclosed after repeated parliamentary questions - be published.
'Ministers cannot claim they are accountable to Parliament when they cannot give us basic information because they say they do not collect it. This is a symbol of the fragmentation of the NHS that the Government's changes are producing.'