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Forty thousand people have signed a Labour Party petition calling for animal testing of synthetic highs to end.
Animal Welfare spokesperson Trevor Mallard said 5000 more signatures were sought before it would be presented in parliament next week.
The petition is a response to the government's move to ban legal highs, which may result in some products being tested on animals in order to prove they are safe. A testing regime has not yet been proposed.
"It's amazing just how strongly people feel about this. The petition was only launched a couple of days ago and the names are rolling in," Mr Mallard said.
"The petition will pressure John Key to stop drug dealers testing highs to be sold in New Zealand on animals either here or offshore," Mallard said.