Australian public servants have been told to anonymously report their colleagues if they are wasting time at work or spending too long at lunch.

The Australian Taxation Office sent out a memo to 20,000 staff in December urging them to be aware of workmates' behaviours, local media reported.

It encouraged staff to report things like inaccurate timesheets or those who read the newspaper for too long.

Critics have denounced the policy as harmful to workplace culture.

The memo began by asking workers: "See something suspicious?"

"You might have seen it before. A colleague makes a habit of taking long lunches, or regularly leaves early, or spends the first hour at work eating breakfast and reading the paper... or all of the above," read the memo, now published on the agency's website.

It urged staff to raise suspicious behaviour with management or internal investigators.

Falsifying work hours constituted "fraud" - something all employees were obliged to help report, the memo said.

Is this kind of surveillance at work helpful?

Not according to unions and workplace experts, who criticised the policy as intruding on privacy and turning employees against each other.

"You're jealous because someone else is away from work... and because you don't like it, you dob them in," Australian Services Union secretary Jeff Lapidos told the Australian Broadcasting Corp in explaining his concern.

Associate Prof Angela Knox, a workplace expert from the University of Sydney, said the policy created a hostile environment.

"This Big Brother-style surveillance is very worrying," she told the BBC.

"If I were an employee I would be thinking that the workplace doesn't trust me and that perhaps I should rethink the trust I have put into the workplace."

She said it would inevitably lead to higher turnover rates among staff and drops in motivation and productivity.

In a statement, the tax office - Australia's main revenue collection agency - said the majority of its workers had complied with its expectations.

"We are proud to have a workforce which seeks to uphold the highest levels of integrity, which the community would expect," it said.

"Integrity is everyone's business and we continually raise awareness of integrity matters with staff."