Workers who faked a sickie in the lead-up to Australia Day have been branded "un-Australian".

Australians have been done out of a long weekend this Australia Day, with the public holiday falling on a Tuesday.

But research shows that up to 500,000 workers will blow off work today anyway to snare themselves a four-day weekend.

The head of the Retailers Association, Scott Driscoll, says people who joined the mass sick day so are un-Australian.

"Those people that are going to selfishly turn their backs on their mates in the workplace and leave the heavy lifting to them and head down to the pub or the beach, they're un-Australian bums," he said.

"Unfortunately there's going to be plenty of them around the country today."

Research conducted by absence-management firm Direct Health Solutions shows that the increase in workers taking sick days today will cost the economy about $257 million.

Nick Behrens, the general manager of policy at Chamber of Commerce and Industry in Queensland, says workers who fake illness today are being selfish.

"If that forecast is realised there certainly will be a significant negative impact on the economy and accordingly we have urged all employees to do the responsible thing by their co-workers and their employers and turn out [to work]," he said.

Mr Behrens says having the day off will hurt employers and contribute to a $30 billion annual sick day bill for the Australian economy.

"Essentially it's money being paid out where there is no productive return for that money and accordingly there are a number of employers that have had to dig deep into their own pockets over the last 12 to 18 months," he said.

"Employers have stepped up over the last 12 to 18 months and done everything possible to ensure that they have not had to let their employees go when there wasn't necessarily the work for them to do.

"That ate into their profits. And them having to fork out for another $250 million at this time, I think, is a little unfair. Ideally the employee would repay some of that generosity and turn up today for work."

Most likely fakers

Union members and mums and dads have been dobbed in as among those most likely to fake a sickie.

"There is certainly a prevalence of absenteeism in a number of areas, call centres or contact centres are obviously exposed in this area," Mr Behrens said.

"Those employees who are union members are more often than not likely to take a day off when they're not entitled to do so.

"Unfortunately younger employees also take more time off as opposed to their older colleagues. And interestingly, and perhaps not necessarily relevant to today, those parents who have children of primary school age are more prone to take a day off as well."

But the Australian Council of Trade Unions says it does not support workers faking sick days.

A spokeswoman for the ACTU says there is no evidence to show that union members fake more sick days than other Australian workers.

"Our view in regards to people taking advantage of this policy to make the most of the weekend is that they should have been up front with their employees and made prior arrangements," she said.

"Unscheduled absentees without medical reason is not supported.

"There is no substantiated evidence that union members take more sick leave today than non-union members and we encourage all business organisations to be responsible when making these kinds of claims."

Workers caught out

For those taking a sick day today, Mr Behrens says their employers are probably onto them.

"There's an interesting statistic that 25 per cent of all sick leave taken on either a Friday or a Monday is not genuine," he said.

"The interesting thing about this is if you ask employers, 75 per cent believe that any sick leave taken on a Friday or a Monday is not for genuine purposes.

"You can see that there's actually a disconnect between employer perception and employee behaviour, so even if there was a worker taking a day off today for genuine reasons, chances are the employer is going to think that employee unfortunately is having an [fake] sick day."

Workers at the Queensland Chamber of Commerce get a gold star for showing up today. Mr Behrens says he is proud of the full turn out in his office.

But he offers a reprimand for workers around the country who didn't show up.

"[Later today] we'll hear about some of the business that have been hit and we feel for them. We think it's unfair and we think the employee is doing the wrong thing by their co-worker," he said.

"Their co-worker will have to stay longer to fill the void. I mean, work has to be done at the end of the day and someone has to do it and if the employee doesn't turn up to do it it leaves someone else in the lurch."

Legally though, those who did not show up today will get away with it and if it turns out they indulge too much tomorrow, they'll get away with taking Wednesday off too.

"In terms of workplace law, the employee if they take more than two consecutive days off, the employer is entitled to ask for a medical certificate. But if it's a one-off like today, chances are the employee's going to get away with it," he said.