Last month the Government announced that employers will no longer have to show their revenue has dropped by 30 per cent to get staff who have to self isolate due to Covid-19 testing on to its leave support scheme. The scheme means workers are paid the equivalent of the wage subsidy.
Unions and health clinics had been worried that people with little or no sick leave were putting off being tested because they couldn't afford the time off work.
CTU president Richard Wagstaff told Morning Report sick leave for Covid-19 needs to be extended until next year.
"We think it should go beyond this because really it doesn't matter whether you've got Covid or you might have it or even if you're got the flu, you shouldn't go to work if you're sick.
"You're likely to spread it around; you're not likely to work properly. We think the statutory minimums aren't sufficient to allow everyone who gets sick to take a sick day and it [instead] encourages them to go to work."
A shortage of sick leave was a problem borne by low-paid workers and the cost to employers of allowing them more would be a cost well worth bearing.
"I think they [businesses] can afford it... most of us probably will never draw on this... I think the benefit outweighs the cost... Covid has really revealed the importance of people staying away from work.
"Remember a lot of people get sick in the course of their work, they're in harm's way. Why should they be penalised financially for getting sick on the job?"
While the proposal had not been costed, the cost of making colleagues ill and the impact on productivity should be factored in.
It doesn't mean every person would take an extra five days, Wagstaff said. It would help those who exceeded top levels occasionally and would also help those who were in their first six months in a job who currently were entitled to no sick leave.
Ten days' sick already exists in many workplaces and he was not aware of it causing a problem. "We don't hear of workplaces wanting to reduce their sick leave."
He is confident the issue will be debated during the election campaign partly because the trade unions will be raising it. He believes Labour and the Greens will support it.