United Utilities plans to keep its service “running as normal” despite a third of its employees planning to go on strike for two days later this month.

Hundreds of workers are due to take strike action for the first time since 1992, according to Unison North West, over proposed cuts to their pension scheme.

Strike action is planned for Friday 16 March and Monday 19 March, which Unison says will “impact the whole of the North West region”.

The union said strike action has been called due to a United Utilities management plan to impose changes to a staff pension scheme from 1 April.

It claims the changes will reduce scheme members’ pensions “significantly”, with younger members of staff “due to lose as much as £10,000 per year of their guaranteed income in retirement”.

A spokesperson for United Utilities told Utility Week: “We are disappointed that Unite, Unison and Prospect have asked their members to walk out for two days. Around a third of employees are involved, and we have plans to keep our services running as normal.

“Many companies have found that final salary pension schemes have become much more expensive to fund and UU is no exception. The costs of keeping our company scheme open are predicted to keep on rising to unsustainable levels.

“The unions helped to shape the final version of the new scheme. Rather than scrap the defined benefit scheme as planned, we agreed to introduce a hybrid scheme, which will cost us considerably more. So, we have made considerable concessions already and hope that the unions will show a similar desire to compromise.”

Vic Walsh, Unison North West regional organiser, said: “The pension scheme is in good financial health and there is no need for these changes to be made.  It is not too late for management to see sense and stop the strike action by halting their plan.”

The union said the water company’s pension scheme was reported to have a surplus of £248 million in March 2017.

It also highlighted more than £1.25 billion was paid out to shareholders over the past five years and claimed United Utilities has a target of increasing its dividend payments each year “by at least the rate of inflation”.

Walsh added: “Our members are asking whether they are being made to pay the costs of the company’s failings out of their pensions.  While executives and shareholders are doing nicely, attacks are being made on the staff who deliver an essential service to the public.  It is wrong that a public utility is being run in this way.”

Speaking at Water UK’s annual City Conference in London last week, environment secretary Michael Gove warned water companies “in the public eye you are very handsomely remunerated.”

He went on to outline “the chief executive of United Utilities [Steve Mogford] is paid £2.8 million per annum.