Nearly half of all employees are unhappy with their pay, a survey of 4,000 workers suggests. Overall, women are less satisfied than men with their pay, the survey carried out by Incomes Data Services (IDS) and the TUC found.
However, women are far more reticent than men to discuss pay with their employers.
Just under two-fifths of women had discussed pay with their boss in the past year, compared to 44% of men.
"In many workplaces, women tend to be in low-paid part-time positions, and the men tend to be the ones earning the biggest salaries," Alastair Hatchett, head of pay services at IDS, said.
"In this kind of environment a low-paid woman is less likely to ask her boss for a raise," he added.
In workplaces without union representation workers were even more unlikely to raise the issue of pay, the survey found.
The TUC and IDS launched an online website earlier this year called PayWizard, allowing workers to check their salaries against people doing similar jobs in different parts of the country. BBC News