Chris Hipkins is urging the government to get on with changes aimed at clarifying the law around sexual consent, rather than making it a campaign issue.

National has promised to make the law clear that there must be consent before sex every time, rather than assuming it has been given, but only after this year's election.

But Labour already has a bill doing much the same already drafted. It was developed by a cross-party group of MPs, and would define consent as something "communicated through words or actions", not silence or inaction, and that a person cannot reasonably believe consent has been given unless they have taken reasonable steps to establish it.

Speaking to Morning Report on Tuesday, the Labour leader said National declined to back the bill, led by Labour justice spokesperson Camilla Belich.

"The National Party decided not to support the bill - all the other parties in Parliament have all indicated they'll support - so that they could go off and delay progress so that they have something to campaign on," he said.

"They could progress the issue right now and a bill could be entered into Parliament right now and progress could be made on it."

Hipkins said Labour would back National's changes, if they were put forward. The Greens likewise, co-leader Marama Davidson saying on Monday it could happen right away.

National justice spokesperson and present Justice Minister Paul Goldsmith on Monday said National was "focused" but already had an "extremely" busy agenda.

"'I've got many changes in relation to retail crime and a whole bunch of things that we've been doing, and we're indicating that if we're re-elected, we'll be changing the law in this space.

"I'm glad that Labour are supportive of it, and I'm surprised they didn't do it when they were in government."

Hipkins did not directly answer the question of why the change was not made when Labour was last in government.