The Greens want Mr Peters, the Deputy Prime Minister and Foreign Minister, to protest to US ambassador Scott Brown about the treatment of children.
On Tuesday, Labour deputy leader Kelvin Davis and National leader Simon Bridges joined an international chorus of opposition to the current practice, saying it was cruel and inhumane.
The closest Mr Peters got to criticism was saying New Zealand would not do what the US did, but he said he wanted to focus on what was happening in New Zealand while he deputises for Prime Minister Jacinda Ardern when she is on maternity leave, not on other countries.
"The mass detention of children and separation from their families as a part of immigration policy is unacceptable," said Golriz Ghahraman, the Green Party's human rights spokeswoman.
"The Green Party is calling on the Prime Minister and Minister for Foreign Affairs and Trade to express New Zealand's opposition to this practice in the strongest possible terms to the United States ambassador," she said.
"We cannot stand by and let this happen.
"New Zealanders take huge pride in our country's record of standing up for what's right on the international stage," she said.
"We must do that now, and use every avenue we can to push the United States to change their policy."
Amnesty International said yesterday that more than 3000 New Zealanders had signed a petition urging the US Government to stop forcibly separating parents from their children at the border.
"The practice is nothing short of torture."
Coincidentally, Ms Ghahraman will move a non-debatable motion in Parliament to mark Refugee Day.
