Alex, 21, says he's "probably guilty" of groping women in the past at clubs but says he's been groped by women.

"I expect I'm guilty of resting my hand on a girl's bum," he tells Newsbeat, admitting it probably used to happen when he was 18 and going out a lot.

"You're inexperienced, and you look at older people and see them groping and you assume it's OK."

New research has revealed almost two thirds of 18 to 24-year-old women expect to be groped at clubs and bars.

Alex, who has two younger sisters, said he started to realise that he and his friends needed to change their behaviour.

He says if they hadn't, they might be chucked out of clubs.

Sexual harassment is illegal and if it had been reported, Alex could have been in trouble with police.

Alex, who's from Newport, says he's now changed his attitude.

"We've all got sisters and all got mothers, so I asked the boys when they were doing it, 'Would you feel comfortable if that was your sister getting approached like that, or your mother or my sisters. Do you feel comfortable watching that or letting someone do that to them?'

"If you wouldn't feel OK with it, then ask yourself, 'Should you be doing that to a girl?'

"After saying that it does kind of work. You don't have to be groping a girl for her to realise you fancy her."

Alex says he's also been a victim of groping and the new research by the charity Drinkaware, which spoke to 1,000 men as well as 1,000 women, found a quarter of men had been sexually harassed on a night out.

"When I've been groped it's been literally anywhere below the waist - front and back."

But he says as a man he feels he can't say anything without getting mocked by his mates.

"It's really uncomfortable not being able to really do or say anything about it.

"It's the same with the bouncers. You can't say, 'That woman groped me.' You just get laughed at and told to 'man up'.

"And when you get laughed at, it makes it 10 times worse."

If you're on a night out and see a friend - or a stranger being sexually harassed - here's the advice from Drinkaware:

1. Spot it - is something dodgy happening?

2. Check it - is it safe to step in?

3. Speak out - if it's safe to do so, check in with the person being targeted. Are they OK? If not, try staff or security.

Find us on Instagram at BBCNewsbeat and follow us on Snapchat, search for bbc_newsbeat