National is ramping up its pre-emptive attacks on a capital gains tax, with leader Simon Bridges saying it would lead to more people leaving New Zealand for Australia.

The Tax Working Group's final report is due out on Thursday and is expected to include some form of a capital gains tax (CGT).

Speaking to media this morning, Bridges came out swinging and said such a tax would come at the detriment to middle New Zealand.

"[It would be] a recipe for more people buggering off to Australia."


But Revenue Minister Stuart Nash rubbished Bridges claims.

"It doesn't seem to make sense. Keeping in mind those who have the means to 'bugger off to Australia' will also know that the Australian top tax rate is 45 per cent and our top tax rate is 33 per cent."

Finance Minister Grant Robertson has ruled out a CGT on the family home, but any other asset classes – such as a farm or a small business – may be in the taxation firing line.

"I think [a CGT] is going to sock it to hard-working Kiwis who play by the rules," Bridges said.

He said it would be small business owners who "slog their guts out", as well as farmers and people saving for their retirement, who would be hit by any CGT introduced by the Government.

"[New Zealanders] pay a lot of tax and [the Government] piles on more. The disincentives on hard-working Kiwis who play by the rules will be there."

Act Leader David Seymour has also come out strongly against any CGT, this morning launching a campaign against any such tax, which he said he would be fighting "vigorously".

Asked about a GCT this morning, Nash said it was about "fairness, balance and integrity of the system".


He said he thought there was a "hole in the system at the moment", but encouraged people to wait until the report is released on Thursday.

Meanwhile, Bridges said the announcement that the Government had begun the process of slapping multinational digital companies, such as Google and Facebook, with a new tax was a "decoy" to distract Kiwis from the Tax Working Group's report.

Nash said this was not the case, and added that the Government had been working on this anyway.

But Bridges said the Government was trying to get people on side with the idea of tax by "slugging it to the multinationals".

But he said if the Government thinks the multinational tax was going to make a capital gains tax more popular – "they are badly out of luck".