Winston Peters has criticised the India Free Trade agreement at its first reading, saying National has "covertly" changed course on migration settings for Indians.

Speaking in Parliament, the New Zealand First leader said officials had discussed the importance of "not announcing these changes for fear of the Indian reaction - this is bad faith".

"We've recently received the evidence in the form of a briefing from officials and consequent decisions made by the Minister of Immigration (National's Erica Stanford) that immigration policy settings are being made more restrictive in a way which targets India and India alone."

He quoted from that briefing, saying officials warned Stanford more restrictive settings would "have impacts on our bilateral and trade relations with India and potentially on New Zealand's reputation as a place to to business".

The officials, he said, pointed to such changes being open to legal challenge.

Peters, who is also the foreign minister, also repeated these claims in a separate NZ First-branded media release shortly after his speech.

He said Stanford had "approved" the "discriminatory treatment" including:

1. Imposing a labour market/economic needs test on Indian citizens but not other relevant FTA partners.

2. Precluding Indian citizens from applying for a temporary employment entry visa from within New Zealand.

3. "Treating Indian citizens worse than the citizens of other relevant FTA partners when it comes to their partners and children".

4. Precluding Indian citizens from counting work experience on a temporary employment entry visa towards residency requirements, a right extended to citizens of other relevant FTA partners.

Peters said NZ First had opposed including any migration concessions in the FTA, and if additional restrictions were being brought in "the only consistent and principled step would be to apply these restrictions to citizens of all FTA partners".

RNZ has sought comment from McClay and Stanford.

Previously, trade minister Todd McClay had talked up the deal, saying it would reduce tariffs on 95 percent of current exports to India, with 57 percent duty free from day one.

"This once in a generation agreement gives our exporters unprecedented access to 1.4 billion people, it will help diversify our export markets and will support the goal of doubling the value of our exports over 10 years."

He said the FTA reflected the strength of the relationship with India and was the start of a "new and exciting chapter" in that, and acknowledged Labour's support for the bill.

Labour's Vanushi Walters similarly commended McClay for completion of the deal, "no doubt building on the work that was done by my colleague the Honourable Damien O'Connor in the last term".