THE gender pay gap has widened over the last four years, according to new research, and there are claims the backwards step has cost women an extra £177 a year.
On the 44th anniversary of the Equal Pay Act, the statistics suggest movement on the issue is heading in the wrong direction.
Campaigners warn that the gender gap means women in Scotland are being paid only around 80p for every pound a man earns.
The new research shows that in Scotland in the eight years between 2002 and 2010, when the Coalition Government came to power at Westminster, the pay gap narrowed by 7.4 per cent.
However, between 2011 and 2013, the latest year in which figures are available, that gap widened again by 0.6 per cent.
Men working full-time in Scotland in 2013 earned an average of £13.28. For women working full-time that figure was £12.22.
On average, when all types of work, including part-time working, were taken into account, men took home £12.70 an hour and women £10.44 an hour.
Campaigners say there are a range of reasons for the differences, including the fact more women work part-time.
But they insist that the pay gap should be diminishing more quickly.
Labour's shadow Scottish Secretary, Margaret Curran, who commissioned the research from the House of Commons Library, claimed that if trends had continued after 2010, when her party lost power at Westminster, then female workers would have been an average of £177 a year better off.
She accused governments in both London and Edinburgh of taking their eyes off the ball,
Speaking to a group of activists in Glasgow today, where she will unveil the figures, she will say: "The Equal Pay Act was a success for the Labour movement across the whole of the UK. From the first women who went on strike in Scotland for equal pay in 1943 to the famous strike at Ford in Dagenham in 1968. But since 2010, progress has stalled.
"Under the Tories, the pay gap in Scotland has started to widen again. And from the SNP and the Scottish Government, we see complacency and a total lack of ambition."
Labour has pledged to introduce "make work pay" contracts to incentivise firms to pay the living wage and to strengthen the minimum wage.
Conservative MP and Women's Minister Nicky Morgan said her government had to take difficult decisions because of Labour's "economic mismanagement".
She added that, across the UK, the fact "we see a near zero gender pay gap for the under-40s working full-time shows we are moving in the right direction and progress has been made since 2010.
"There is more to be done but this government is proud there are more women in work than ever before and that we have taken 1.5 million women out of having to pay any tax. These measures are part of the long term economic plan to secure Britain's future."
A Scottish Government spokesman said it had a "strong record on closing the equality gap between men and women".
He added: "The gender pay gap is lower in Scotland than UK as a whole and the other devolved nations," he said. "We are aware more must be done.
"That's why we continue to fund Close the Gap to change employment practices and workplace cultures and Equate Scotland to encourage more women to get involved in the science, technology and engineering."
The Chartered Management Institute (CMI) last year warned male managers had earned on average bonuses twice as big as those of their female counterparts over the previous 12 months.
Figures released earlier this year by HM Revenue & Customs showed self-employed women also earned around 40 per cent less than self-employed men in 2012.