Parliament's Security and Intelligence Committee will hear public submissions in secret on a bill that strengthens the laws covering the Security Intelligence Service (SIS), Prime Minister John Key says.

Mr Key introduced the bill today, saying the legislation hadn't been updated for 40 years and the SIS needed laws that were "relevant to the global security environment" in which it operated.

It updates the warrants framework, especially around electronic tracking devices and computer surveillance, and technology like mobile phones and cyber identities.

Mr Key said it did not change the threshold for surveillance warrants, and he did not expect a change in the number of domestic warrants issued each year which at present ranges from 11 to 15.

He said the committee would call for public submissions on the bill after it had been given its first reading on Thursday.

"The public can make their point to the committee in person and in writing," he said.

"They will be heard in private."

Mr Key said he didn't know whether there was a precedent for that, but those who made submissions would be free to publish them if they wanted to.

"It won't be in the public interest to have it open, for a whole bunch of reasons I don't want to go into," he said.

Mr Key said that while submitters could make their submissions public, the interchange between them and the committee members needed to be in closed session.

It is within Parliament's rules for that to happen and it is up to the committee to decide whether to hold open hearings.

Mr Key is the chairman of the committee and its members are Deputy Prime Minister Bill English, Labour leader Phil Goff and representatives of minor parties.

Speaking at his post-cabinet press conference, Mr Key said that for reasons of national security he did not intend going into detail on why the SIS needed the legislative update, but next year's Rugby World Cup was one of them.

"We obviously need to make sure that we provide all the national security that is appropriate," he said.

"We're not predicting instability but we have to have the right legislation in place."

He said part of the reason for updating the bill was that the SIS needed specific laws, not general ones.

"From a legal perspective, this is driven by the fact that developments in case law means there is an expectation for any search and seizure by state agencies to be supported by express provisions in legislation," he said.

Those laws already covered the police and customs, and the SIS was being brought into line with them.

The Green Party said the Rugby World Cup was being used as an excuse to extend SIS powers.

"The main security problem for the World Cup will be drunken fans, which is best dealt with by restricting the supply of alcohol, not restricting our civil liberties," said MP Keith Locke.

"It is a pity there wasn't any advance public consultation on the proposed changes - the SIS culture of secrecy at all costs prevented this."