HUNDREDS of workers across three unions have begun strike action at Scottish Water as their pay dispute escalates.

The four-day walkout by members of Unite, Unison and GMB is the first phase is what could be 48 days over the next three months.

The dispute centres upon pay and the effective imposition of a regrading, which workers argue undermines their unions as well as collective bargaining agreements at the Scottish government-owned company.

Tension at the company deepened when it emerged that three executives on the board imposing the regrading had taken home six-figure bonuses last year.

In a question to the First Minister on Thursday Scottish Labour’s Pauline McNeill challenged the fairness of the bonuses when the “same executives are withholding a pay rise from their workers unless the staff accept a new pay structure.”

Defending the company, First Minister Humza Yousaf argued the bonuses would “attract and retain highly experienced personnel to run a vital public service,” adding that he hoped talks would avert the strike.

His hopes were not shared by Unite general secretary Sharon Graham however, who branded talks “a waste of time” while the company insisted on “foolishly” linking pay to the regrading.

She said: “It appears to be the case that the bosses in the boardroom will only listen to us when our members have taken to the picket lines across Scotland.”

Ms Graham’s sentiments were shared by Unison’s Emma Phillips, who has labelled Scottish Water a “rogue employer.”

And GMB’s Claire Greer said: “Its actions over the last six months are a template for how to demoralise staff and demolish industrial relations.”

In a statement, Scottish Water Chief Operating Officer Peter Farrer said: “We regret that the unions have decided to take industrial action. Scottish Water remains committed to reaching an agreement.”