The pay gap between men and women has narrowed since the national minimum wage was introduced but the difference is still 19 per cent, new Government research shows.

Average earnings of women in the year to March were 81 per cent of men's, around one per cent lower than the previous year. Average hourly earnings for full-time women workers increased by three per cent in the same period while for men it was two per cent.

Campaign groups such as the Equal Opportunities Commission are calling for more urgent measures to tackle the gender pay gap.

More than £2.2 million in underpayments has been won for workers since the minimum wage was introduced in April 1999.

There was speculation that if the minimum wage was linked to average earnings, the figure could rise from the current £3.70 an hour to £4 an hour next year. Ministers are understood to favour a link with the growth in average earnings rather than inflation, arguing that the rate should keep pace with wages as it is not given as a benefit.