Delegates at the union's local government group conference in Bournemouth passed a resolution calling for the agreement to be renegotiated - a move welcomed by the National Union of Teachers (NUT), which said both unions could now make 'common cause (to) achieve common objectives'.
The Unison resolution said the Government had made it impossible to implement the agreement by imposing 'standstill' budgets. It added, 'Unison's response to this dishonesty must be to acknowledge that remodelling has been a failure.'
The vote surprised Unison officials as it coincided with publication of a union survey that indicated a 'marked improvement' in the role of support staff.
Unison's head of education, Christina McAnea, said that although 90 per cent of local education authorities in England and Wales had set up local remodelling groups, 'local negotiations are still lagging behind what's happening in schools'.
The survey, which covered 750 schools and more than half of the local authorities in England and Wales, found that nearly two-thirds of schools have increased the number of teaching assistants and that one in five LEAs had created a new career structure, with three in ten of these at an 'advanced stage'.
But the NUT said the workload agreement was 'falling apart'. The union also backed the call for support staff to be employed on permanent contracts.
The NUT has written to headteachers and chairs of governors at every school in England and Wales urging them not to jeopardise their children's education by using 'unqualified staff' to teach.
The Unison resolution had noted that 'the experience of the remodelling agenda underlines the argument of those in this union who saw it as an attempt to use our members to provide teaching on the cheap'.