ESTELLE Morris, a week into her government's second term in office, has been threatened with a renewed High Court battle with the National Union of Teachers over performance pay.
The NUT has warned the education secretary that regulations which allow school governors to use teacher appraisal results to set pay levels are unlawful.
General secretary Doug McAvoy suggested that the Government was trying to "con" teachers.
Ministers now face a choice between ploughing on with the changes, and thereby risking a court battle, or referring them to the already-overloaded School Teacher Review Body.
But this week the review body's chairman publicly complained to Ms Morris about the amount of "minor, technical or incidental" work his panel of volunteers was being asked to do.
However, a spokeswoman for the Department for Education and Skills said the regulations had already been in place for most teachers since last September.
"It's hard to understand why the NUT is challenging arrangements which have been in place for nearly a whole academic year and offer such benefits to their members," she said.
NUT lawyers picked up the faults when the DFES decided to tweak the regulations to include teachers employed by local authorities.
Governors have limited discretion over pay. They can award management points and allow high-flying junior teachers to jump a year as they move up the pay scale. In rare cases they are also allowed to hold underperforming staff back a year.
But they will soon be making decisions on rises for experienced staff who have crossed the threshold. Ministers plan to extend their powers still further by giving successful schools the right to opt out of the national teachers' contract.
The NUT won a High Court battle last yar over performance pay, arguing that a new duty on teachers to appraise their colleagues had been introduced unlawfully. The victory delayed the introduction of the threshold by several months.
Ms Morris is already dealing with an unprecedented rebuke from Tony Vineall, chairman of the School Teachers' Review Body. He said the government was involving his organisation, consisting of volunteers and a small secretariat, in minor technical details on teachers' pay so frequently that it was "in danger of damaging (the body's) primary role".
He wrote: "Many of the detailed issues could, in our view, be more appropriately dealt with by consultation with the parties."
His comments are all the more damaging because the review body has been widely seen as too compliant with government wishes. But sympathy for it was this week muted. The National Union of Teachers said the body had "thrown in the towel".
The STRB's main job is to produce an annual report with recommendations on teachers' pay and contracts. It can also be called on to look into "urgent" matters, such as changes to the contract thrown up by the NUT's successful High Court challenge over performance pay.
Employers backed the STRB's complaints. Graham Lane of the Local Government Association called the present set-up "absurd".
Unions, however, said the letter heralded a return to some form of collective bargaining. And Mr Vineall hinted that the Department for Education and Skills could already be looking at re-establishing direct negotiations with unions.
"I imagine that you and officials may already be considering options of re-establishing a more workable framework which avoids the problems I have outlined," he wrote to Ms Morris.
A DFES spokeswoman said ministers were aware of the review body's concerns. "We will want to consider this carefully and discuss it with the STRB."