Gareth Morgan's new political party already has more than 880 paid members - with the entrepreneur saying he has been blown away by the response.

Morgan launched The Opportunities Party (Top) on Friday, saying problems like inequality and housing affordability could be solved but not by "establishment" politicians.

He plans to gauge public reaction to his campaign before registering the party next year.

Political parties need 500 financial members to register, and that mark was surpassed by Top within 24 hours of launching. As of Sunday afternoon the party had 886 members signed-up.

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"I've been really overwhelmed by the response," Morgan wrote in a blog post today.

"I thought would take us months to get those kinds of numbers, particularly given I haven't released any policy yet!"

The reaction from established political parties has been mixed, with both Green Party co-leader James Shaw and Prime Minister John Key saying it will be difficult for Top to get the 5 per cent of the party vote required to enter Parliament.

At the 2014 election, Craig's Conservative Party received 95,598 votes and still fell short at just under 4 per cent of the party vote.

Top will release about six key policies, with the first a housing-related policy on December 8. If public support looked to be forthcoming, the party would aim to register in March.

A trained economist, Morgan amassed a fortune after selling his economic forecasting firm Infometrics in the late 1990s, later set up Gareth Morgan Investments, and received a windfall after a $75,000 investment in Trade Me, set up by his son Sam, turned into $47 million.

Morgan pledged to give away the millions earned through his Trade Me investment, and established the Morgan Foundation, which focuses on conservation and development projects as well as public policy research.

Most controversial was a 2013 campaign to eventually eradicate domestic cats - or "sadists" and "natural-born killers" - with Morgan wanting people to not replace the pets when they die.

Morgan has resigned as a trustee of the foundation to head the new political party.