David Cameron was accused of deepening divisions in the health service by only inviting royal medical colleges and health practitioners that he believes will back his NHS reorganisation to a special summit at Downing Street on Monday.

Strikingly it appears both the BMA and the Royal College of General Practitioners have not been asked to the summit, even though the transfer of greater powers to doctors is a centrepiece of the changes.

Cameron, facing widening opposition to the reorganisation from across the health service, sections of the Liberal Democrats, crossbench peers and fellow Conservative cabinet members, believes he has no alternative but to plough on with the health bill, and show there is a viable support base for the changes within the health service.

But Lord Owen – who has long argued that the position of the royal colleges will be critical to the bill's fate – accused Cameron of "reprehensible tactics". The doctor and former foreign secretary said: "He is clearly trying a policy of divide and rule in the hope that he can break the opposition to the bill by only asking those he believes will support him. The health service is based on much more integrated team work these days right across from nurses, doctors, commissioners and clinicians, and this is not the way to treat an integrated health service. A divided health service cannot function effectively.

"The prime minister may think he can outmanoeuvre or override the BMA in the same way that Clement Attlee and Aneurin Bevan did when the 1945 Labour government introduced the National Health Service in the face of opposition of the BMA. But the BMA in 1946 was much more evenly divided than they are now and Attlee had a clear electoral mandate from the British people to push through his reforms – something Cameron does not have."

Owen claimed Cameron was putting intense pressure on the Royal College of Physicians (RCP) not to come out against the bill.

"I think there are some royal colleges that will be attending today, such as the Royal College of Physicians, that should say they do not support meetings being organised by the prime minister in which sections of the health service are excluded."

The RCP has invited its 14,000 worldwide members to an extraordinary general meeting in London on 27 February to discuss its approach to the bill, and whether to seek the views of members in a survey. The Royal College of Surgeons – long-standing supporters of the bill – have been invited.

Downing Street refused to discuss the precise guest list of the meeting, except to acknowledge that it is built round supporters of the reorganisation, which still needs to complete the report stages in the Lords.

Cameron's aides stressed that the meeting was purely about how to implement the health bill, and was not a discussion about potential concessions.

It was also openly asserted that those chosen to attend the summit had been selected on the basis that there was little purpose inviting the kind of groups that had opposed the changes from the outset.

Cameron will tell the summit that patients are already beginning to see the fruits of greater GP influence in areas where clinical commissioning groups have been set up.

He will point to evidence that emergency hospital admissions have fallen year-on-year for the first time, as GPs have been made more central to shaping care for patients and the NHS has moved away from Labour's "targets" culture to the coalition's emphasis on "outcomes".

Department of Health figures show a 0.5% decline in emergency hospital admissions in 2011, compared with a 36% increase between 2001 and 2010.

The health secretary Andrew Lansley said: "We have always been clear that patients will benefit from putting power in the hands of frontline doctors and nurses. By starting to do just that, we are seeing a positive change in the way our NHS is responding to rising pressures.

"Patients are being treated in more convenient places, pressure on hospitals is reducing, and we are safeguarding the NHS for future generations."

The government has tried to simplify its often over-complex story on the health changes by honing the key message to a statement that they will reduce bureaucracy and put GPs in the driving seat.

The refusal of the BMA and the Royal College of General Practitioners to support the changes will be counter-balanced by the evidence that GPs are already introducing them and that they are already working.

It will also be stressed that the BMA is conducting a negotiation over its pensions, and may even call a strike.

The shadow health secretary Andy Burnham said Cameron had "got this one wrong" and urged the PM to invite the BMA, Royal College of Nurses, Royal College of Midwives and Royal College of General Practitioners, all of whom oppose the bill. "People have strong and sincerely-held views about the risks to the NHS from the government's reorganisation," he said "They deserve a hearing – not to have the door of Downing Street shut in their faces."

A poll for the trade union Unite, conducted by YouGov, suggests six times as many people trust health professionals over the prime minister and the health secretary on NHS reorganisation. The survey also shows 68% of those polled want the government to publish its own risk register on the changes.