The Prime Minister is under pressure to take a harder stance on Saudi Arabia's human rights record during his historic visit to the country.
John Key arrived in the Gulf nation last night, to try to get some progress on a stalled trade agreement with the Gulf Cooperation Council.
Negotiations for a deal with the Gulf states ended in October 2009, but it was never signed off.
Resistance from Saudi Arabia was a stumbling block to passing it.
Opposition MPs said he had a duty to raise concerns about Saudi Arabia's human rights abuses, ahead of any trade deal.
Green Party co-leader Metiria Turei said human rights issues and violations should be part of any deal.
"To have an honest relationship with these countries, then we need to be open with them about our expectations."
She said Saudi Arabia had an appalling human rights record; beheadings, lashings of women who had been raped, and torture of children.
Labour Party deputy leader Annette King said John Key needed to spell out what human rights issues were raised in his talks.
She said those rights needed to be part of any negotiations.
United Future leader Peter Dunne said he had little regard for Saudi Arabia's human rights record, but a trade deal was a good idea.
"That is in New Zealand's interest but at the same time, just as we should with China and other countries who have reprehensible practices, we shouldn't feel cowed in that process from speaking out against what we regard as pretty barbaric behaviour."
New Zealand First leader Winston Peters was worried any agreement would be one-sided.
"There are cultures coming into New Zealand that are not paying nearly enough respect to the nation's laws and belief in freedom of religion," he said.
Mr Peters said if a trade deal with the Gulf Cooperation did not specify what was expected of them in New Zealand, then it would fall short.
He said trade deals needed to be beneficial to all parties involved.