The Advertising Standards Authority has ruled the Conservative Party breached its code of ethics in an election pamphlet targeting New Zealand First leader Winston Peters.
The authority said the party made a substantive error of fact on its claims about alcohol reform.
Its pamphlet suggested Mr Peters would not support the five key recommendations of a Law Commission report into alcohol but the Conservative leader Colin Craig would.
The authority's Complaints Board said the Law Commission report actually contained more than five recommendations and this part of the ad would have misled consumers.
However, both party leaders are declaring the ruling a win.
Mr Peters said Mr Craig was misleading voters with incorrect information by cherry-picking what he said were five key recommendations in the report, which is about 40 pages long.
But Mr Craig said authority dismissed the vast majority of complaints from New Zealand First and the Conservatives have to make only one small correction on some wording. He said the New Zealand First leader did not complain about any of the central facts.
The leaders have traded shots throughout the election compaign over policy and both have been trying to woo the same elderly vote.