There is doubt from the Opposition that the Customs service has the ability to use proposed - and controversial - new powers to search travellers' electronic devices.

Legislation will go before parliament later this year giving Customs Officers the power to access travellers' electronic devices. It would be an offence for people to deny access.

Currently, when Customs examines a person's electronic device the owner is not legally obliged to provide a password or encryption key.

The agency says if people refuse, it can leave no way to uncover evidence of criminal offending even when officers know the device holds that evidence.

Customs' preferred option was to require passwords for electronic devices without meeting a threshold, such as suspicion of criminal activity.

Labour MP Rino Tirikatene said you're treading on dangerous ground when you seek such access and cites privacy protections people have.

But he said the bigger issue is Customs' ability to use the proposed powers "let alone try and identify who may have a device that they want to crack into."

Minister of Customs Nicky Wagner said Customs has been asked to do further work and report back before legislation is introduced to parliament.

"We want to make sure that the wording is correct," she said. "We want to make sure that the process is simple. We've got protections and that. We're not expecting it to make much change to what's happening now."

Wagner insists the new powers are not something people should be afraid of.

"It something that's been brought to people's attention so they think it could be frightening but we get very few complaints, we look at very few numbers of e-devices, and actually we catch people doing illegal things on them."

Critics of the proposal, including the NZ Council for Civil Liberties, have cited what they see as serious workability issues around the proposed change to require passwords, including the fact a person can have documents or files in cloud storage, meaning they will not be kept on an electronic device.