Sally Hunt, general secretary of the University and College Union, has written to members at 67 universities asking them to work to contract from 10 October.

The industrial action is over changes to the ?30 billion Universities Superannuation Scheme, whose 130,000 members are mainly academics and senior administrators in pre-1992 universities.

The changes include putting new members on lower-value, career-average pensions and capping the inflation-proofing of all pensions.

The UCU balloted 39,400 of its members over the plans for "sustained" industrial action. All those balloted will be eligible to take part.

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On the initial action, Ms Hunt says that members should "work no more than your contracted hours where those hours are expressly stated" (or not exceed the maximum hours "stipulated in the Working Time Regulations") and should "perform no additional voluntary duties".

If that fails to bring the employers to the negotiating table, the union will organise "rolling strike action within each institution with different groups of staff taking turns to take action in order to cause maximum disruption", Ms Hunt says. The next step would "include a boycott of the REF and student assessment".

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The union's legal advice is that employers will not have the right to deduct pay from employees working to contract because they are performing their minimum duties.

But Ms Hunt warns that "members should be aware that the (Universities and Colleges Employers Association) recommends to its institutions a far more hard-line approach to participation in industrial action than other public sector employers".

A Ucea spokesman said: "Employers are extremely disappointed by this latest attempt to take industrial action that would undoubtedly damage students. Staff are members of a very good USS pension scheme, with modest changes having been agreed according to the scheme's own rules."

john.morgan@tsleducation.com.