The Government has said there could be changes to regulations, but not the law governing genetically modified organisms.

It comes as the Environmental Protection Authority's approved the release of a GMO called Pexa-Vac for a medical clinical trial for treating a type of liver cancer.

It's the first GMO treatment that's ever been approved which is capable of reproducing itself.

Otago University genetics director Dr Peter Dearden said viruses could be genetically modified to kill cancer cells and leave normal cells alone.

"This is just the tip a of an iceberg, these approaches that are coming on the market or being developed."

The organism would be unlikely to survive outside the human body.

Environment Minister Nick Smith said our current GMO laws are cautious, and a lot more cautious than those in many countries.

He said a blanket ban is inappropriate and they don't have any proposals to change the law.

"There are some refinements on things like the regulations that we need to be open minded about while ensuring that we're protecting the public. We take a cautious view, but we do realise that biotechnology offers benefits to the public."

The Greens are calling for some independent evidence before giving a blessing to a GMO release that's been approved for a medical clinical trial.

Green MP Steffan Browning said he's cynical about the assurances the EPA has made about it being low risk, but he wouldn't like to stand in the way of effective treatment for individuals and this looks like it has the potential for that.

"What I'm looking for is some robust analysis by some genuinely independent and capable scientists who add to the discourse that has been had at the EPA."