Headteacher unions have sounded the alarm that a no deal Brexit could be “extremely damaging” to teacher supply.

According to new guidance published by the government last Friday, if Britain leaves the EU without reaching a deal, the current system whereby professional qualifications are automatically recognised across the European Economic Area will cease to apply.

Teaching is one of the professions covered by the ‘mutual recognition of professional qualifications’ directive – if someone qualifies as a teacher in an EEA member state, they can apply for QTS in England.

However, the government’s guidance states that if there’s a no deal, then after March 2019 the directive will “no longer apply to the UK”, and the UK will have to put in place a new system which will “differ from the current arrangements”.

“EEA professionals… who have not started an application for a recognition decision in the UK before exit will be subject to future arrangements, which will be published before exit day,” the guidance says.

Headteacher unions warned that uncertainty over the procedures for letting foreign teachers practice in the UK would be bad for schools.

Geoff Barton, general secretary of the Association of School and College Leaders, told Tes: “Any additional barriers to recruiting teachers from overseas would be extremely damaging to the already precarious teacher supply situation in this country.

“The fact that the latest data shows we recruited nearly 5,000 teachers from European Economic Area countries in 2015-16, shows just how significant this source of staff is in ensuring that we have enough teachers in our schools.

“They are particularly vital in respect of modern foreign languages where we have a dwindling supply of home-grown teachers, and these subjects would become even more difficult to sustain if recruits were deterred by a new layer of red tape.”

Paul Whiteman, general secretary of the NAHT heads’ union, said: “We know that recruitment is a real problem for schools at the moment, so anything that adds uncertainty or an extra layer of complexity will be a real headache for school leaders."

A Department for Education spokeswoman said: “We recognise the important contribution to the UK made by professionals from the European Economic Area – across all sectors, including teachers.

"Our new arrangements for the recognition of professional qualifications will ensure that professionals from Europe will have a means to seek recognition in order to work in the UK. More details will be released in due course.”