Since delivering the Budget in May, Finance Minister Grant Robertson has been in demand on the speaking circuit. On Wednesday, about 40 business people, party faithful and lobbyists paid $600-a-head to hear him speak at the exclusive Wellington Club.

Finance Minister Grant Robertson gave a post-Budget speech at a $600-a-head Labour fundraiser at the exclusive Wellington Club, drawing comparisons to the previous National Government's "Cabinet club" scandal.

According to several attendees, about 40 people, including party supporters, business figures and corporate lobbyists, attended the dinner hosted by Labour president Nigel Haworth on Wednesday, at which Robertson was the key attraction.

A similar dinner is due to be hosted at the even more exclusive Northern Club in Auckland on Thursday night.

SIMON MAUDE/STUFF Labour Party President Nigel Haworth has defended Robertson's attendance at the party fundraiser, saying he was there in his capacity as an MP, not as a minister.

National leader Simon Bridges has accused the Government of hypocrisy, after Labour once described National's events, which appear similar to the one attended by Robertson, as "cash-for-access".

READ MORE: Does Cabinet Club buy influence?

The concern is that wealthy figures are able to gain access and insight that is not available to the general public.

HAGEN HOPKINS/GETTY IMAGES National leader Simon Bridges has accused the Government of hypocrisy after "Labour sought to kick the crap" out of National for similar events during its time in Government.

Events such as this also come close to the line in terms of the rules for ministers.

The Cabinet manual states: "holding ministerial office is regarded as a full-time occupation and is remunerated as such. Accordingly ... accepting additional payment for doing anything that could be regarded as a ministerial function is not permissible".

This means that if Robertson was attending in his ministerial capacity, rather than as an MP, Labour would be unable to use the event as a fundraiser.

STUFF The exclusive Wellington Club was the venue for Labour's fundraiser on Wednesday. Founded in 1841, it is New Zealand's oldest private club, and owns an elegant seven-storey building on The Terrace in central Wellington.

A spokeswoman for Robertson refused to make any comment, describing the dinner as "a party matter".

The Prime Minister, who is charged with ensuring Cabinet rules are being adhered to, has also refused to comment.

At the Wellington Club dinner, Robertson spoke about May's Budget and future Budgets. He also signalled policy announcements set to be announced in the coming weeks, one person who attended claimed.

Another person at the dinner described Robertson as "extremely on message". After his speech, Robertson went table to table for more private conversations with small groups.

Haworth said, as Labour president, it was his right to invite any party member to a dinner.

The dinners were part of a series of events Labour ran and $600 was the standard price, he said.

He refused to reveal how much profit the party made from the event, saying "that's for us to know".

Haworth said Robertson should not be speaking about party matters, given he was there as an MP, not finance minister.

"He was there, invited by me, as a senior member of the party."

Shortly after the story was published, an invitee supplied Stuff with a copy of the invitation sent out by Haworth, which suggested Robertson was at the event as finance minister.

"You are cordially invited to join me at a private post-Budget dinner with the Finance Minister, Hon Grant Robertson MP."

Earlier, he insisted that Robertson's speech was "about the economy, much more generally" rather than the Budget, before adding that "of course the Budget came into it".

Wednesday's Wellington Club dinner was the first of its type since the election, Haworth said.

LABOUR JUST LIKE NATIONAL?

While in Opposition, leading Labour MPs described revelations about National's "Cabinet club" – where supporters paid large sums to hear ministers speak – as a "cash-for-access scandal".

No one from Labour has attempted to draw a distinction between Robertson's dinners and the National Party events.

Both National and Labour have justified the events as saying ministers attend the events in their capacity as MPs, rather than as ministers.

But Labour has previously mocked the distinction. Labour MP Nanaia Mahuta, who was a minister in the Clark Government, said in 2014: "In my experience of that position, you are a minister at all times, day or night."

Haworth said guests at the dinner "mainly" saw him. "We tailor the speaker to the audience very much, or back, to the theme, very much."

Two people who attended said Haworth simply introduced Robertson and David Talbot from UMR, Labour's polling company.

Haworth did not believe those attending gained influence over Robertson.

"I have no reason to believe that's the case. There's never been an example or evidence given to me that it is the case."

BRIDGES: NATIONAL 'LEARNT A LESSON'

National leader Simon Bridges accused Labour of hypocrisy.

"Labour sought to kick the crap out of us for somewhat similar sorts of events. Now they're deep in it."

It was "deeply ironic" that Labour was giving speeches at the venues Robertson was speaking at, Bridges said.

"All this talk in the election campaign and recently about the squeezed middle and equality and the need to do more with urgency in the way that supposedly - although I disagree - National wasn't. Then they're highfalutin it at the fanciest clubs in New Zealand at big prices per plate."

Bridges said the average New Zealander probably would not understand what it meant for a minister to be at an event in a personal capacity.

"I'm not having the Labour Party on for having fundraising events. Parties do need to do it, and there is a line here that I appreciate is fine, around ministers versus MPs and those Cabinet rules issues," he said.

"I think the National Party learned a lesson around Cabinet Club and the like and changed our policies accordingly. But [Labour] were the guys who had us on about it. They're doing the same thing, at high prices, in the fanciest clubs in the land."