The first major potential trust school sponsor revealed its plans to The TES this week, but warned that ministers need to offer schools financial incentives to join the controversial programme.
The news that CfBT, a not-for-profit organisation, wants to create a trust supporting as many as 35 schools is good for the Government which is expected to publish the education bill next week.
Apart from Churches considering tweaking the status of their existing schools, it has until now failed to secure a major public commitment to trust schools from an external organisation.
But Neil McIntosh, CfBT chief executive, will have tempered any joy by urging ministers to reconsider the politically difficult issue of extra funding for trust schools.
There is also potential for long-term difficulties, with CfBT wanting to use freedoms to change staff pay and conditions, something the National Union of Teachers last week said could lead to industrial action.
Headteachers' leaders have also warned that restrictive PFI contracts may also create difficulties for sponsors.
Mr McIntosh said CfBT was keen to get involved. But he is concerned that trust schools will be funded at the same level as foundation schools.
He wants an analysis of schools' money retained by local authorities to see if there is scope for more to go directly to trust schools.
"There needs to be some incentive for heads to go the trust school route and I don't think there is much at the moment," he said.
But giving trust schools, billed as independent state schools, preferential funding would bring them almost into line with the former grant-maintained schools created by the Conservatives, something ministers facing a backbench rebellion have been anxious to avoid.
Meanwhile there are concerns because existing PFI contracts would transfer directly to new trusts, restricting their flexibility.
Schools are already finding that such contracts can make it difficult for them to rent out their space or extend school hours.
John Dunford, general secretary of the Association of School and College Leaders, said sponsors would want as much flexibility as possible. "A PFI contract transfer is going to be a major complicating factor," he said.
Mr McIntosh said that without further incentives he expected the trust school programme to progress very slowly. "We would have to demonstrate that we could provide a school with something it didn't already have," he said.
CfBT, which runs Lincolnshire and East Sussex councils' school improvement services (see below), would offer schools centralised expertise through its trust.
In 1998 the company became the first to take over the day-to-day running of a state school at Rams Episcopal primary, in Hackney, east London. The contract finished a year later with the school still failing and CfBT claiming that the local authority vetoing its staffing choices undermined its chances.