Secondary school teachers have unanimously supported a motion to cease working additional hours agreed under the Croke Park pay deal, raising the prospect of industrial action and school closures this autumn.

The move, if approved by a ballot of the union’s membership over the coming months, would place teachers on a collision course with the Government and could result in teachers losing out on thousands of euro in pay increments.

Delegates at the annual convention of the Association of Secondary Teachers in Ireland (ASTI) voted on Wednesday morning to stop working an additional 33 non-teaching hours per year.

Under the Croke Park deal agreed in 2010, teachers are obliged to work these hours which are mostly used for staff meetings.

Under financial emergency measures agreed by the Government, financial penalties could be placed on teachers who do not co-operate with these productivity measures.

A succession of branch members told the convention that these extra hours were a “petty and vindictive” move which were undermining time that could be spent on extra-curricular activities or class preparations.

Mary Ohle, a delegate from the union's Dublin north-west branch, said the hours were demeaning to the profession.

“They are incurring extra childcare costs and are viewed as detention for teachers,” she said.

James McGovern, a delegate from Enniscorthy, said the additional hours were a "ludicrous and unnecessary imposition" and were a PR stunt for those who believed teachers had easy jobs.

Noel Buckley told the conference that the additional hours were undermining teachers' ability to engage in extra-curricular activity such as drama, music and sport.

“One of the main reasons we resent these Croke Park hours is the fact it’s the Department of Education saying we don’t trust you as professionals,” he said.

ASTI general secretary Kieran Christie said the union had received legal advice that any move to cease working Croke Park hours would require a fresh ballot of members later this year.

He said the union had been advised that any repudiation of the Lansdowne Road agreement could result in a freeze in pay increments over the next two years, worth over €2,000 in some cases .

“I raise these matters because the likelihood is that they are going to be a major item on our agenda later this year,” he said.

“And there is no shortage of variables that we cannot predict. We don’t know who will be in government or who will be minister. We will also have to see if we can make common cause with the TUI. But as I say it will be a big ticket item for us this year.”

Delegates, however, voted to reject a motion calling on members to cease working 43 hours of supervision and substitution.

Teachers are due to receive payments for these duties, worth about €1,600, in September.

Mark Walshe said that voting to cease supervision and substitution duties could risk payments due to teachers in September and lead to school closures.

He said a more effective approach was to cease working those hours if the Government did not pay sums due to the profession.

“Let them (the Government) be the aggressor,” he said. “If they don’t pay, they’ll be in breach of the agreement.”

Noel Buckley also warned against “opening a war on two fronts” and said the union should prioritise the restoration of a common pay scale for newly-qualified teachers.

The ASTI, along with the TUI, say the Haddington Road agreement - which succeeded the Croke Park agreement - expires at the end of June of this year.

Both have rejected the Lansdowne Road agreement on public service pay - the successor to Haddington Road - which was backed by a majority of public service unions last autumn.