The Preschool Learning Alliance initially welcomed nursery vouchers - until it discovered that playgroups would receive only Pounds 550 for each part-time place.
This dashed the PLA's hopes that voucher money would help playgroups to improve quality and increase the number of sessions.
The PLA also fears the outcome of the initiative would be unpredictable because of its reliance on market forces. Although it supported the Government's aim of creating Pounds 165m of new places in the first phase, it feared progress would be limited without investment.
Provisional registration for accreditation will be allowed if playgroups agree to work towards a set of "desirable achievements for children's learning, " to be considered by Ministers in November.