The measure is "an attack on democracy" according to an emergency motion carried unanimously at the Association of Teachers and Lecturers conference.
Earlier ATL general secretary Mary Bousted called the plan "madness".
On Monday, School Minister Nick Gibb said the plan made schools "profession-led" - though he faced some heckling.
Under the plan almost 17,000 schools which have not already converted to academy status - mostly primaries - must do so by 2020 or have committed to do so by 2022.
Delegates applauded as the ATL became the third teachers' union to oppose the plans.
The conference, meeting in Liverpool, voted to condemn the White Paper, Educational Excellence Everywhere, as "an attack on democracy".
Proposing the motion, Mark Baker said White Paper's proposals amounted to "Educational Excellence All Over The Place".
The motion warned that conversion of schools to academy status would be achieved without regard to the wishes of parents, staff or local communities and without proper Parliamentary scrutiny.
The move represented "ever greater centralism and micro-management".
"It takes no account of the growing evidence of failing academies but insists on a blind adherence to an ideology with no foundation in fact," said the motion.
The ATL will now work with "all those concerned", including other education unions to opposed forced academisation and to consider what forms of action - including potential industrial action - may be needed.
In her speech to conference on Tuesday morning, Dr Bousted backed calls for a co-ordinated response.
"Alone we can do something. Together we can do great things.
"We must fight together to protect our profession, for the sake of the children and young people whose education depends on us.
"And we will fight and if we fight together, with parents and councillors, with other unions, with politicians, with governors, with the whole of civil society which opposes the madness of forced academisation, then we will win," Dr Bousted concluded.
Earlier in the speech Dr Bousted called the white paper a "very strange document".
"It asks us to believe six impossible things before breakfast, including the big whopper - that the forced academisation of all schools will improve educational standards."
The government's plans have drawn criticism from teachers, unions and Tory local councillors.
At its conference over Easter, the National Union of Teachers  voted to ballot for strike action over the academies plan.
The NASUWT conference also voted to consider strike action if forced academisation affects members' pay and conditions.
The Labour Party has said its own analysis of official figures suggests the plan could cost £1.3bn with a shortfall in funding of  over £1.1bn - though ministers reject these figures.
But in a speech to the NASUWT Education Secretary Nicky Morgan said there was no going back on plans to make every school an academy by 2020.
Ms Morgan maintained the government's plans would improve the education system in England.
The Department for Education said it was "disappointing that the ATL would rather play politics with our children's future than work constructively with us to deliver our vision for educational excellence everywhere".
The "vast majority" of schools which had already became academies were "now thriving", said a spokesman.
The spokesman said figures from 2015 showed sponsored primary academies open for two years had improved their results by an average of 10 percentage points since opening - more than double the rate of improvement in local authority schools.
One of the most moderate teaching unions has voted for industrial action over government plans to force all schools in England to become academies.