Teachers are being urged to write to their MPs, asking them to sign a Commons motion against plans to allow hundreds of schools to become academies.
The NUT is asking teachers from all unions to contact their MPs to support the Early Day Motion, which was tabled by Labour MP Jon Trickett.
The motion says there are "serious concerns" about plans to confer power to governing bodies, "without proper consultation with parents, school staff or the local authority".
It adds that the Government's invitation to "outstanding" schools to become academies will result in "further disadvantage to already disadvantaged children and families".
The plans would "raise fundamental issues such as loss of local democratic accountability, excessive cost, lack of fairness and administrative confusion", it says.
The motion has already attracted the signatures of 12 MPs, including Labour's Glenda Jackson, Dennis Skinner and Jeremy Corbyn.
Meanwhile, the leading teaching unions have also written to headteachers and governors warning them against rushing into becoming academies.
The letter to heads warns that the unions hold a "common belief that academy status would bring neither you nor your school greater freedom, nor reduced bureaucracy, nor any long-term financial advantages".
Urging teachers to write to their MPs, Christine Blower, general secretary of the NUT, said: "We must do all we can to oppose the threatened huge expansion of the academy programme."