Senior academics are refusing to act as external examiners – a vital part of higher education assessments – in protest at pay and working conditions in UK universities, and are urging colleagues to join them, potentially disrupting this year’s results for students.

British universities rely on external examiners to independently validate the results of undergraduate and postgraduate courses, meaning that mass resignations would cause headaches for universities in the setting and marking of exams.

A letter to the Guardian signed by 29 professors said they were resigning as external examiners and refusing to take on new contracts because of pension cuts and insecure contracts throughout the sector, as well as gender and ethnicity pay gaps, heavy workloads and stress.

“We are refusing to act as external examiners because although we believe that this role is crucial in underpinning the quality of education provided to students, so too is the need to provide fair pay, pensions and job security for those who work in universities,” the letter states.

“It is long past time for universities to address these festering problems, and we believe we have a responsibility to staff at the start of their careers to make a stand now. Please join us by resigning external examiner posts and refusing to take on new contracts until universities take action to address these issues.”

Phil Taylor, a professor of work and employment at the University of Strathclyde, said he had signed the letter because he was “fed up” with universities treating their staff with contempt.

“Someone starting now is likely to have to deal with one insecure contract after another, face cuts in their pension, spiralling workloads, unrelenting pressure, soaring stress levels and pay inequality. Universities must start to value staff more or they will lose what little goodwill that is left,” he said.

Another signatory, Natalie Fenton, a professor of media and communications at Goldsmiths, University of London, said British universities boasted about their global reputation while treating staff as second-class citizens.

“It is really important that senior academics on established contracts make a stand in support of less fortunate colleagues. I will be refusing any invitations to act as external examiner for degree courses until universities address these issues,” Fenton said.

External examiners are experienced academics such as professors or senior lecturers, who give independent assurance that a university’s assessment system is fair and help to maintain rigorous academic standards.

The external examination boycott comes during industrial disputes at many British universities, with the University and College Union leading a strike at 60 institutions last year and more strike ballots being held this month.

“External examiners resigning their positions, and refusing to take up new ones, are very serious steps and demonstrate the huge levels of frustration that exist,” said Jo Grady, the UCU general secretary.

“External examiners are vitally important both to protecting educational standards and to the sector’s academic reputation but they want to support colleagues who face pension cuts, insecure contracts, spiralling workloads and pay inequality.

“Universities must now recognise the strength of feeling that exists across the workforce and make substantial changes in the way they treat staff or they will undoubtedly face not just further industrial action, but also more withdrawals of cooperation.”

A spokesperson for the Universities and Colleges Employers Association said the protest “does not seem to reflect accurately the issues” in the current industrial disputes.

“Many universities have also been in dialogue with their unions over the wider employment issues that have been packaged in to one of these disputes and it is wrong to assert that there is any unwillingness within universities to discuss and address these issues,” the association said.

A spokesperson for the industry body Universities UK said: “It is right that university staff should expect good working conditions, fair pay and an attractive pension. This is what universities are striving to provide.”