GENDER GAP: Wellington teacher Alan Proctor-Thomson enjoys a coffee from a cart which is highlighting the gender pay gap by charging men 10 per cent more than women.

Coffee will cost 10 per cent more for men than for women at Wellington's Victoria University Law School campus this morning.

In an effort to highlight the continued lack of pay equity between men and women, a campaign by the YWCA is calling on Parliament to do something about the problem.

A coffee cart has been set up on the Law School lawn this morning, which was as close as organisers could legally get to Parliament grounds, to illustrate the issue in real terms.

Long blacks and flat whites would cost $3.50 and $4 respectively for women, while the same drink would cost $3.85 and $4.40 for men.

It was an easy way to demonstrate to people that the gender gap was unfair, YWCA national executive officer Steph Fink said.

The ''Demand Equal Pay'' campaign aims to persuade Government to introduce the Pay Equality Bill, drafted by Dr Judy McGregor into Parliament for its first reading.

Wellington teacher Alan Proctor-Thomson said he was passing by when he saw the stunt and instantly knew what it was about.

''It's a great campaign. I think it [the pay gap] is completely wrong so this is probably a fair deal.''

Mr Proctor-Thomson said he was not sure how he would feel if there were gender-driven price differences in everything he bought.

Organiser Lisa Fedyszyn said she wanted men to understand the issue and be just as outraged as women were. ''If the percentage isn't zero then it's not fair.''

Ms Fedyszyn said the coffee cart had also featured in Auckland, where many men had resorted to getting their wives or girlfriends to buy their coffees for them.

Pay Equity Challenge Coalition spokesperson Angela McLean said the campaign was timely, because there were new figures showing the gender gap had widened from 12.85 per cent in September last year to 14.18 per cent at the same time this year.

"We need the Government to own up to the problem. We won't build a stronger economy and fairer society without valuing the contribution of women, and a real commitment to equal pay and pay equity."

The coffee cart will be at the Law School lawn until 11.30am.