The Mana Party is joining the parliamentary inquiry into ways to protect manufacturing jobs.
Labour, the Greens and New Zealand First announced the inquiry on Friday and with Mana's inclusion it now covers all the parties in Parliament except National and its allies ACT, United Future and the Maori Party.
Opposition parties made their move after government MPs blocked a bid for a select committee inquiry into the manufacturing sector and why there have been a string of redundancies.
Exporters say they are being crippled by the over-valued New Zealand dollar and are calling for government intervention.
So are opposition parties, and they want the Reserve Bank to be given new powers so it can control the exchange rate.
Trade unions, opposition parties and manufacturing sector organisations attended a summit meeting on Friday to discuss what they say is a crisis in the sector.
Prime Minister John Key says it isn't in crisis, and he wouldn't have attended the summit even if he had been invited.
Mana Party leader Hone Harawira says a financial transactions tax would bring the dollar down.
"We believe that one of the primary reasons for our dollar being so high is because our currency is one of the most traded in the world," he said today.
"A financial transactions tax is being supported by 11 European countries including France, Germany, Italy and Spain - the Greens are behind it and Labour hasn't ruled it out."