He said the party had been banned from leaders' debates on TVNZ and Radio NZ, and ignored by the Herald, Dominion Post and Christchurch Press.
"But despite this disgusting behaviour, on election night this party will hold the balance of political responsibility," he told the audience of around 50.
Mr Peters will likely see more airtime in the lead-up to the election, after TVNZ decided to invite Mr Peters to their minor leaders debate because his party received 2.9 per cent in the latest One News Colmar Brunton poll.
TVNZ made its decision on including Mr Peters in the debate before Mr Peters' speech this morning.
The New Zealand First leader is also due to take part in a live chat with nzherald.co.nz readers next Tueday at midday.
However, Mr Peters slammed the media for "censoring" the party's policy announcements.
"We have been shut out. We have been blocked out by TVNZ, as you well know. We've been blocked out by [the New Zealand Herald], day after day you have published the various parties' policies, you've deliberately excluded New Zealand First.
"New Zealand First has always known, that no matter what ban and what vetting, censoring and non-reproduction of our policies and speeches happens, we slog it out around the countryside as we have, that we would make it back. We are confident of that."
Mr Peters said the party's policies resonate with a lot of voters.
"We've got the record for opposing asset sales - the others have not. We've got the record for arguing for savings in this country - the others have not. We have got a record for arguing for an export-led recovery and the policies to bring that about - the others have not. But the biggest reason is we have always stood for one New Zealand and one law for everybody. And those are the reasons this party is coming back.
"We've packed a lot of halls and that's what in the end demonstrates the market demand for what we are saying. The fact that our speeches have not been published, the fact those speeches have been totally omitted from media communication does not alter the fact that in the end those people coming to those meetings represent the market demand for what this party stands for.
"We have access to three very important running polls on which we rely. That has given us cause for enormous confidence and our supporters have never wavered in believing what we can achieve in this election."
Mr Peters is not the only one who believes New Zealand First will be back - Act Party Epsom candidate John Banks also reckons they will return to Parliament.
Mr Banks said the polls are closing - and he believed Winston Peters will end up with more than five per cent on election night.
He told Newstalk ZB that when Labour does poorly the centre-left smaller parties like New Zealand First do well.
