The Birmingham and Solihull PCT cluster 'fairer funding plan' will move 69 PMS practices to a standard price per patient of £72.91 over the course of three years.
The current average payment for PMS practices in the area is £81.55, with top earners receiving up to £115.86.
The PCT has estimated that once the standard payment is in place in 2015, the maximum loss faced by a practice would be £135,000 a year. On average, practices face losses of nearly £82,000.
GP leaders have warned that income for both GMS and PMS practices is already falling as expenses rise and pay remains frozen. The GPC said this month it opposed calls from the DH for the independent Doctors' and Dentists' Review Body (DDRB) not to give advice on a pay uplift for 2013/14 (GP, 5 September).
Birmingham LMC executive secretary Dr Robert Morley warned: 'Practices might look at shedding staff. There is a very genuine risk that some salaried GPs might be made redundant.'
He said cuts may push practices to return to a GMS contract without MPIG support, even though it would mean a reduction in funding. 'At least then there is the guarantee of a national contract,' he said.
Laurence Slavin, a partner at specialist medical accountants Ramsay Brown & Partners, said it was inevitable that PMS reviews would lead to practices cutting staff.
'Most practices run efficiently. You're not going to save thousands by skimming the surface.'
Cuts could also force GPs to refer more patients to A&E and increase appointment waiting times, Mr Slavin added.
GPC deputy chairman Dr Richard Vautrey said PMS reviews were a national problem. 'They are certainly something that almost all PCTs have engaged in and PMS practices have suffered significantly.'
A Birmingham and Solihull PCT cluster spokeswoman said: 'An equality impact assessment has been undertaken and it is our view that the programme of work will promote equality and patients will benefit from fairer funding to PMS practices.'