GPs will walk away from the Government's NHS reforms in England unless ministers change rules opening the health service up to more competition, one of the leading architects of the new system has warned.
Dr Michael Dixon, interim president of NHS Clinical Commissioners, said family doctors risk getting "bogged down" in the process and may feel it is "a waste of time".
Meanwhile, more than 1,000 doctors and nurses have appealed to MPs to force a vote on the new rules - known as Section 75 regulations - to prevent their implementation at the start of next month.
The signatories, who include Dr Clare Gerada, chairman of the Royal College of GPs, and Professor John Ashton, incoming president of the Faculty of Public Health, said the regulations will "force virtually every part of the English NHS to be opened up to the private sector".
Labour has tabled a motion in the House of Lords designed to kill off the regulations, which would bar "any restrictions on competition that are not necessary". Critics fear they will make it easier for independent providers to get contract decisions overturned if they feel they should have been open to tender.
But Health Secretary Andrew Lansley told the House of Commons that the regulations do not represent any change from the reforms approved by Parliament last year in the Health and Social Care Act.
The new rules will enable clinical commissioners "to go for... whoever is best placed to deliver to their patients the best service, to improve the quality of the service, to meet the needs of people who use the services and to improve efficiency" and would not require competitive tendering in every case, he said.
Dr Dixon told Pulse magazine: "The danger about the current wording of Section 75 is that it seems to put a duty upon the commissioner to go for competition with all contracts that are made. We don't want to get CCGs (clinical commissioning groups) bogged down in protracted processes. The aim of clinical commissioning was to innovate, to redesign, to try and ensure that we do more outside of hospital and in primary care.
"Now, if that is their aim and they start getting bogged down in matters of issues of whether or not they are being competitive, that is going to take their eye off the ball. Unless the commissioner is king, the system is going to fall down. And worse still, the clinicians will walk and feel the whole thing has been a complete waste of time."
Dr Dixon warned that CCGs may have to defend claims from private companies for not having put service procurement out to tender. "It is going to make everyone watch their back and a whole industry of people who challenge things back and forth as to whether they have been sufficiently competitive or not, and opens the window to providers to challenge the CCGs," he said.