Workforce reform is severely damaging the professional status of teachers, according to the former head of policy of one of the unions signed up to the Government deal.
Meryl Thompson was head of policy at the Association of Teachers and Lecturers when the union signed the agreement which cuts teachers'
She now believes that the reduction in workload does not compensate for "de-professionalisation" caused by the blurring of responsibility between qualified teachers and support staff.
Primary teachers, who are overwhelmingly female, are affected most by the changes, writes Ms Thompson in an article in the latest edition of the education journal Forum.
While most secondaries can provide teachers with non-contact time, primaries can do so only by asking assistants to take whole classes.
"Workforce remodelling has undermined the professional status of qualified teachers," she writes. "It will continue to challenge both the security and the identity of teachers wherever and whenever there is pressure on resources.
"In particular, it has the potential to destabilise the supply of primary teachers and to demoralise primary practitioners, notwithstanding a reduction in workload if they perceive their skills and expertise - their investment in their pre-service training and graduate education - are undervalued and are not quantitatively differentiated from those of teaching assistants."
The workforce agreement was signed by the Government, employers, support-staff unions, headteachers and the ATL and NASUWT unions in January 2003.
It promised teachers reduced workload by delegating administrative tasks to support staff and by guaranteeing them the equivalent of half a day per week of non-contact time for planning, preparation and assessment.
In return, the signatories agreed to support the use of teaching assistants to take whole classes.
The deal was rejected by the National Union of Teachers, the largest teaching union. It argued that the agreement would damage the profession.
The National Association of Head Teachers quit the so-called social partnership with the Government last year because of concerns that there was not enough money to put the deal into practice without compromising standards.
Both the NUT and the NAHT have been frozen out of policy discussions with the Government as a result of their opposition to the agreement.
John Bangs, the NUT's head of education, said unions involved in the social partnership had lost their ability to defend their members' interests in key areas independently.
"The social partnership agreement has redefined the meaning of social partnership away from the meaning commonly understood elsewhere in Europe.
(It) subordinates all parties into a single corporate identity."
Meryl Thompson retired as head of the ATL's policy unit in 2004 but continues to serve as a school governor.
The ATL declined to comment.
Forum is available from www.wwwords.co.ukFORUM