NHS Worcestershire is revising existing premises contracts with 10 practices and inserting a new requirement for 'improved performance'.
One practice in the south west of England has agreed to achieve performance indicators demanded by its PCT. If it fails to meet the targets, the GPs will forfeit £30-40,000 a year.
Another practice in the south central area is negotiating a deal in which it guarantees to stay in the top half of practice performance indicators for its PCT to pay the rent on new premises.
'It's getting impossible to get premises development money without strings attached,' said GPC member and Wessex LMCs chief executive Dr Nigel Watson.
'It's blackmail and once it starts it will continue. We advise practices not to sign up to these agreements but the rules do not stop PCTs from trying to impose conditions.'
NHS Worcestershire director of primary care, Dr Jonathan Leach, told the PCT's board this month that the cost of new premises 'has to be offset by savings generated by the practices'.
But he denied the PCT was blackmailing practices.
Facing budget cuts of £60 million over three years meant it had to prove expenditure offered value for money, he said.
The PCT wanted to invest in practices, but needed to justify the spending by demonstrating a link to high performance and making the case that this would help practices take on more work, he explained.
'It is the realpolitik of where we are,' he said. 'It is not blackmail. Our approach is to have a discussion with practices and meet in the middle.'
But Worcestershire LMC secretary Dr Simon Parkinson said: 'To link new surgery development with reductions in referral and prescribing rates is unfair and sets a very bad precedent.'
The GPC's practice finance subcommittee is due to discuss links between premises funds and performance targets next week. Chairman Dr Russell Walshaw said: 'It's arm twisting and blackmail. It's up to the LMC and practices to resist this.'