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Education Secretary Bridget Phillipson said "any move towards industrial action by teaching unions would be indefensible".

They have to support industrial action in a formal ballot before that can happen, and enough of them have to vote.

A spokesperson for Cardiff University called the industrial action "disappointing", and said it will inevitably cause disruption to students.

He said that members are "incredibly reluctant to take part" in any form of industrial action, but the "university is leaving us no choice".

The industrial action, which began in January and escalated to an all-out walkout in March, has seen hundreds of Birmingham's refuse workers on strike.