A plan by the Rudd Government to guard against cyber attacks on sensitive computer networks by allowing bosses to spy on their workers' emails and internet communications was like "cracking a walnut with a sledgehammer".

The Opposition, privacy and civil liberties groups slammed the proposal yesterday, saying it would lead to an unnecessary invasion of individuals' privacy.

Federal Attorney-General Robert McClelland said the Government would consult widely on what was just a proposal at this stage, which would look at excluding the use of personal information. He pointed to a cyber attack on government computer systems in Estonia, which he said effectively shut down the Government for up to two weeks, as the impetus for the proposal.

The plan was to draft laws dealing with employees in critical industries vulnerable to cyber attack by computer hackers.

The Opposition appeared divided on the subject, with leader Brendan Nelson saying while the idea had some merit, he was worried about the privacy implications. But Dr Nelson's workplace relations spokeswoman, Julie Bishop, and legal affairs spokesman, Senator George Brandis, both attacked the proposal as placing an unnecessary burden on employers to do the work of ASIO and the police.

"Employers should not be burdened with the responsibility of intercepting emails involving staff suspected of behaviour that threatens Australia's national security," Ms Bishop said. "This places an unfair surveillance responsibility upon employers ..."

Vice-president of the NSW Council for Civil Liberties Pauline Wright said it would be like using "a sledgehammer to crack a walnut" and allowing email snooping by bosses was open to abuse.