Meanwhile, ACT Education Minister Joy Burch said the union was not negotiating in good faith as she had personally offered to reinstate the back-pay if teachers signed the new Enterprise Bargaining Agreement, worth 12 per cent over four years.

Australian Education Union ACT secretary Glenn Fowler said teachers were furious at the current state of negotiations, and accused Ms Burch of attempting to "blindside teachers by withdrawing back-pay of salary increases."

Ms Burch said the union was aware that by rejecting the pay offer last October it had missed the deadline to receive back-pay.

Yet she said she had personally offered to get a variation to the cabinet decision to ensure back-pay was part of any new deal.

"Frankly I am getting frustrated by Glenn Fowler's selective memory on the issue," Ms Burch said.

"I am not opposed to back-pay being delivered, in fact I am supportive, but Mr Fowler has not asked me to activate my offer."

But Mr Fowler countered he had not received that offer and teachers could not be expected to sign a deal based on a verbal assurance from the minister.

"Contrary to what Minister Burch has attempted to lead the Canberra community to believe, the second offer to ACT educators actually takes money away. The three per cent per annum offer will only begin after an agreement is signed instead of being backdated to October 2014. This makes the first year offer closer to 0.5 per cent than three per cent.

"This is a used-car deal that teachers will certainly see through. This is an insulting attempt to punish teachers for rejecting the partial, incomplete and unsatisfactory offer in October last year. ACT educators are not likely to be intimidated by Minister Burch's tactics."

While teachers were likely to broadly accept a pay offer of 12 per cent, the contentious issue remains the number of face-to-face contact hours they undertake.

Education Director-General Diane Joseph said the offer included a minimum of 20 hours per year reduction of workload for every teacher in the ACT public system.

"With this offer the ACT Government has sent a clear signal that it has listened to and values its teachers," Ms Joseph said.

"The government is taking the initiative to clearly articulate its commitment to the core role of teachers – that is teaching students. Through this offer there will be clear guidance on tasks that are expected of teachers, tasks that require limited teacher involvement and tasks that do not require teacher attention."

The directorate has promised to identify a teacher's core role, monitor workload and "make time during normal hours for quality professional learning focussed on teacher practice in the classroom".

Mr Fowler said the directorate had failed to demonstrate how it would fund those workload reductions.

"The ACT Education Minister has been presented with objective evidence from the Australian Council of Educational Research that ACT teachers are working an average of 50 hours a week, well in excess of the national average. Yet she has failed to offer a serious solution. While she talks about relieving teachers of administrative tasks, she is not prepared to provide any resourcing to employ other staff to pick up this work.

"There is a basic incoherence at the centre of the minister's position: She says she'll take administrative work off teachers, but she won't say who will do that work instead."