Performance-related pay for teachers has been defended in the High Court, on the second day of a teachers' union's legal battle against the government's pay reforms.

Rejecting claims from the National Union of Teachers that the system of assessments for higher pay was divisive, the government's lawyers presented the pay reforms as fair and reasonable.

The NUT claims that the Education Secretary, David Blunkett, has over-stepped his powers in the introduction of the appraisal system for deciding which teachers should qualify for a performance-related pay rise.

The High Court has heard that the union was "gravely concerned" by a pay system which required all staff to assist in assessing colleagues.

Such a process of assessment would be likely to create "conflict and division", the court heard from the NUT's lawyers.

But the government's lawyers rejected such an interpretation, asserting that the assessments would in practice be carried out by heads of department and other appropriate staff.

"The head teacher has got to act reasonably and cannot at a whim demand a teacher's assistance," said David Elvin, representing Mr Blunkett.

The union wants the court to require the education secretary to remain within his statutory powers on the duties required of teachers and the rules for performance pay assessments.

The hearing was adjourned until Thursday.