She is one of 750,000 Australians working second or third jobs as result of high underemployment according to the latest Australian Bureau of Statistics. There has been a 9.2 per cent increase in secondary jobs compared to a 6.8 per cent increase in main jobs for the past three years.

After nine-and-a-half years in a cleaning job, Ms Allan says she was thanked for her good work, given a glowing reference and dismissed in August last year.

Six months later, only $73 of her redundancy package remained after her regular mortgage payments were deducted from her savings. "I was really struggling," she said.

Now aged 52, she has two cleaning jobs in Melbourne and does two hours of gardening for three clients every fortnight to supplement her income.

She spends two-and-a-half hours cleaning at a school from Monday to Friday. She has another private cleaning job which gives her an extra 10 hours of work a fortnight.

"I would prefer longer hours but I can't take on other work because I finish one cleaning job at 1pm and have to be at the school at 3pm," she said.

"It's really hard to get a full-time job for the day. So I have had to get three jobs to make ends meet because I've got a mortgage and two teenage boys. I've always worked hard. I just take whatever I can get."

Ms Allan says after being made redundant from her job in Ringwood last year she was replaced with another cleaner.

"The only time I missed work was when I had breast cancer treatment. I had the operation in December and went back to work in January, had chemotherapy and radiotherapy and only had one day off after that," she said.

"I was a permanent part-time which meant that they had pay superannuation and sick leave and holiday pay which I hardly took.

"They didn't explain why I was made redundant, they just said you did a fantastic job."

Australian Council of Trade Unions president Ged Kearney said the growth in second and third jobs was "extremely disturbing and should have every Australian worker, economist and politician worried".

"What this shows is that people can no longer survive on a single job," she said. "Working people are rapidly falling into the new class of working poor."

Natasha Lay from Youth Action, a peak body for youth services, said casualisation was impacting particularly on young people who were competing for fewer jobs and more hours.

"Young people are having to work two, three, four jobs that are often unstable," she said. "They need job certainty and job security."

Alan Oster, chief economist at NAB, said there was more slack in labour market than the 5.9 per cent unemployment rate would imply. The underutilisation rate - the combination of unemployment and underemployment - was much higher at about 14.4 per cent.

"There is a lot of slack in the labour market. In that sort of environment it is hard to get a pay rise," he said.

"The unemployment and underutilisation rate usually move together. The unemployment rate is falling but the underutilisation rate is not."

Mr Oster said people were more cautious with their spending because they were feeling less secure in their jobs.

"If you have two part-time jobs you probably feel less secure than if you have one full time job," he said.

The Reserve Bank of Australia has raised concerns about the high rate of people who would like and are available to work more hours.

In a recent bulletin, it said underemployed workers could dampen wage growth because they offered extra labour supply or may be more concerned about their job security and had less bargaining power to get higher wages.

Chris Goodwin, 48, who lives in Kingsford said he could not afford a mortgage in Sydney.

He has worked at Coles for eight years night-filling groceries and has a second job with Uber Eats. He also works as a landscape gardener but finds the work is seasonal.

"There seems to be more people doing Coles as a second job to supplement their income," he said.

"I need to work not just Coles but have to supplement my income because I have three older kids and lots of outgoings.

"Coles covers my rent each week basically and Uber Eats helps pay for the bills and food. Not much gets saved."