A survey of 1,500 women found a third had been subjected to unwelcome jokes and a quarter experienced unwanted touching, researchers from the UK's Trades Union Congress (TUC) and the Everyday Sexism Project found.
Around one in eight women reported unwanted sexual touching of their body or attempts to kiss them at work, which the report's authors point out would be considered sexual assault under UK law.
"How many times do we still hear that sexual harassment in the workplace is just a bit of 'banter'? Let's be clear - sexual harassment is undermining, humiliating and can have a huge effect on mental health. It has no place in a modern workplace, or in wider society," she added.
The TUC found that in nine out of 10 cases the perpetrator was male and nearly one in five women (17 per cent) said it was their line manager, or someone with direct authority over them.
More From This Section
Reasons given included fear that reporting would affect their relationships at work (28 per cent) or their career prospects (15 per cent).
Nearly a quarter (24 per cent) of those who did not report abuse said it was because they felt that they would not be believed or taken seriously and 20 per cent said they were too embarrassed.
The proportion of women facing harassment is higher among the youngest workers - nearly two-thirds (63 per cent) of the 138 women aged between 18 and 24 surveyed said they had been sexually harassed at work.
They were also likely to be in more junior roles, all of which may be factors in sexual harassment, said the TUC.
The TUC commissioned online polling from YouGov of 1,553 women who said they would be willing to respond to questions about sexual harassment.
A UK government spokesperson said: "No one should experience harassment or abuse of any kind in the workplace - the law on this is very clear and employers must take swift action to tackle this issue.
"Section 40 has not been scrapped and any employee who experiences harassment is protected by the Equality Act - regardless of who the perpetrator is," it said.