Green MP Julie Anne Genter says she didn't think TOP could be serious asking her to jump ship.

Senior Green MP Julie Anne Genter says she has rebuffed an approach by Gareth Morgan's The Opportunities Party (TOP) to jump ship.

But the fledgling party denies any "formal" approach was made.

Genter said she had rejected the proposal, made about a month ago after her bill to legalise medicinal cannabis was drawn from the ballot.

She would not disclose who made contact on Facebook, but said it was not Morgan or TOP deputy leader Geoff Simmons.

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"I got a message from one of their senior people, a Facebook message, asking if I could talk. This was about four weeks ago the day my bill got pulled from the ballot so I thought it was about that."

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She had supplied her phone number and he called and said, "Do you want to come over and join us."

"And I said 'you can't be serious' - no I think I said 'you're not serious' and then he said 'I'm dead serious Julie Anne'."

TOPs was seeking a candidate for Auckland Central and he said she was a great performance and "evidence based" so right up TOP's alley.

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She said she had told him her "evidence-based" reasons for staying with the Green Party. It was the best way to make the policy changes she and the caller wanted. That was by changing the Government and the Greens would be a large part of that.

They had discussed a poll that had put the Greens on 9 per cent and TOP on 1 per cent.

She believed that showed TOP was within the margin of error and it would waste some votes - and that the Greens would do a lot better than that poll.

"I said 'nothing personal, I like some of your guys policy and I think we want similar outcomes in terms of action on climate change and reducing inequality and poverty in New Zealand'."

She had also said the Green movement was "way bigger than me, way bigger than one person" and she believed in it.

She had revealed the approach to columnist Toby Manhire who had referred to it but not name her.

It was a friendly conversation that she did not intend to be "a big deal" and did not expect it to be public even though she had mentioned it to Manhire.

"I didn't expect him to use it, no. But, hey, I told him. I was open about it. i just didn't think it was a story."

She said TOP was struggling to get any high profile candidates other than Morgan.

But Genter said she had done nothing to spark the approach.

"I was actually really, really surprised that they would think I would consider it a good move - a realistic option."

TOP's spokesman Sean Plunket said he did not believe a formal approach had been made.

"We certainly haven't had an on the record conversation with her, but if she wants to jump we'd take her ... if she feels she wants to join a party that propogates evidence-based policies and has a fresh approach to politics rather than stay with a party that has been in Parliament for 20 years and has made only marginal gains in areas they were initially interested in."

He could see why she might want to jump ship, but there had been "no formal approach to Julie Anne Genter".

He had talked to her about "lots of things" but he did not have "any record of any conversation where that was discussed".

"We'd be happy to have Julie Anne rather than have to run against her in Epsom."

He said TOP had talked to "lots of MPs" but had not approached anyone to jump ship.

"I can't help it if Julie Anne is fantasising about joining the TOPs party, can I?"