As the News of the World scandal deepened yesterday, authorities urged people to ensure they had rigorous password protection in place.

Most of the hacking in Britain occurred through mobile phone voicemail accounts that could be accessed from other telephones, media reports say.

These ''remote access'' voicemail accounts are offered with most mobile accounts, and often come with a default personal identification number that relates to the phone number.

If users don't change their default PIN, they could be vulnerable to hackers.

The chief executive of the Australian Communications Consumer Action Network, Teresa Corbin, said she was not aware of any complaint about this type of phone hacking.

But she said phone companies had no obligation to tell people if they were aware of personal information falling into the wrong hands.

''The greatest problem with a privacy breach is actually knowing that it's happened,'' she said.

There are laws to protect mobile users from hackers. A spokesman for the Attorney-General, Robert McClelland, said breaking into someone's voicemail without their knowledge was prohibited, and punishable by up to two years in jail.

Anyone who accessed information through hacking is also prohibited from publishing that information.

''Australia has robust laws in place to protect the privacy of users of the telecommunications system,'' the spokesman said.

The Australian Privacy Commissioner, Timothy Pilgrim, said the Privacy Act required governments to keep people's personal information secure, but it did not govern the actions of private individuals.

''I strongly encourage people to make sure that they are vigilant in changing their voicemail passwords regularly to reduce the likelihood that their voicemail can be accessed," Mr Pilgrim said.

The chief executive of the Australian Mobile Telecommunications Association, Chris Althaus, said the type of hacking used in the News of the World scandal was seen as a lower threat than breaking into people's social networking accounts.