A union has called on universities in Scotland to break an impasse in talks about changes to staff pension schemes.

The University and College Union (UCU) said a "sustained campaign" of industrial action by its members would affect nine of Scotland's universities from Monday.

UCU members will be "working to contract", including their obligation to perform their duties in an efficient manner.

The approach will mean the staff will not work overtime beyond their contracted hours.

The move could also include not providing additional cover for colleagues who are off, staff not attending some meetings or working weekends if those actions are not stipulated in contracts.

UCU warned that if the approach does not force negotiations then the action would escalate to rolling strikes and a boycott of student assessment, which could affect up to 100,000 students.

The dispute is about changes to the Universities Superannuation Scheme (USS) pension scheme.

UCU said scheme members are "furious" that changes they "vehemently opposed" were imposed on October 1.

The union said the changes will see staff pay more to work longer, with less protection should they lose their job.

Sally Hunt, UCU general secretary, said: "We are keen to resolve this dispute as quickly as possible with minimal disruption.

"However, you cannot negotiate with an empty chair. The university employers have tried every tactic in the book, from slick PR and misleading adverts to direct intimidation and legal threats against union negotiators.

"If they had focused just a fraction of the time they have spent trying to force these unpopular changes through on negotiating properly, we would not be in this position.

"We want to negotiate and hope those universities keen to avoid unnecessary confrontation and disruption will start to apply pressure on those refusing to talk."

It is understood the negotiations over changes to the USS, which is a private scheme, started more than three years ago.

The changes were approved by the Joint Negotiating Committee (JNC) and then the USS Trustee Board.

Both the JNC and the Trustee Board involved UCU representation.

Responding to the accusation that the university employers used "direct intimidation and legal threats against union negotiators", an Employers Pensions Forum (EPF) spokesman said: "This seems to misunderstand the process that the USS Trustee Board, not the employers, undertook to ensure negotiations were carried out according to the scheme's own rules."

The EPF was established by GuildHE, the Universities and Colleges Employers Association (UCEA) and Universities UK in 2007 as a forum for higher education (HE) institutes to discuss current and longer-term pensions issues, and to develop a strategy that will help the HE sector to continue to offer staff access to high-quality pensions schemes.

Speaking about the UCU action, a UCEA spokesman said: "Employers are, of course, extremely disappointed by UCU's plans to take industrial action.

"The changes to the scheme were approved by the USS Trustee Board, which includes UCU representation, on June 9.

"This followed exhaustive negotiations and consultation. The changes would be considered moderate by many as they include the retention of a final salary pension for all existing USS members. Many will be confused by UCU's position."

UCU said the nine universities where the action would be taken included the University of Edinburgh, the University of Glasgow, the University of Dundee, The University of St Andrews and the University of Aberdeen.