The TUC has thrown its weight behind teaching unions' concerns that the proposals still link pay too closely with results.
The move comes after delegates to the TUC's congress in September backed a National Union of Teachers' motion against "payment by results and performance-related pay for schoolteachers".
The motion had the support of the National Association of Schoolmasters Union of Women Teachers, the Association of Teachers and Lecturers and the Welsh teaching union UCAC.
The Green Paper proposes that teachers who cross the threshold would receive a pound;2,000 rise and move to a new performance-related pay scale. The School Teachers' Review Body is expected to give its verdict on the plans next month.
The TUC has also echoed concerns over funding for teachers to progress up the post-threshold scale, and about arrangements for those moving between schools.
In a letter to Education Secretary David Blunkett, TUC general secretary John Monks, said: "I am very concerned that there is a tight timetable in which the review body is expected to report and decisions are expected soon." Mr Monks is seeking to broker a meeting between the unions and the minister.