Melbourne businesses may need to subsidise rents for hospitality workers as rental affordability in the inner city rises further out of reach, experts say.

The December Rental Affordability Index, released on Wednesday, showed 12 suburbs were severely unaffordable for hospitality workers – with rents up to 60 per cent of incomes – while a further 60 suburbs were classed as unaffordable, with rents between 30 and 38 per cent of incomes.

Rents would have to be lower than 15 per cent of a household income to be affordable and between 20 and 25 per cent to be acceptable, the biannual report, released by National Shelter, Community Sector Banking and SGS Economics, showed

Suburbs including Melbourne CBD, Fitzroy, Richmond and South Melbourne were severely expensive for a hospitality worker on an income of $55,000, and others such as Rosanna, Oakleigh East and Maribyrnong were found to be unaffordable.

More affordable housing in the inner and middle suburbs was needed to avoid not only financial stress and homelessness, but adverse effects on businesses, National Shelter executive officer Adrian Pisarski said.

“People in the part-time economy – hospitality or retail or any kind or part-time employment – are really finding it hard,” Mr Pisarski said. “It puts enormous pressure on how well businesses can run, I think we’ll see employers having to subsidise workers’ accommodation so they can live close enough.”

He said when rents were unaffordable, it affected people’s health and well-being, causing other societal problems.

“Once you pay for housing costs you’re really seeing people doing without appropriate medical care, food and certainly any discretionary spending,” he said. “It is integral to the functioning of our cities and our economy that we have a range of affordable housing.”

Devon LaSalle from Tenants Victoria said rents outpaced wages between 2006 and 2016, with people working in part-time and low-paid jobs most affected.

“The median income has increased by about 35 per cent but the median rent has increased by over 75 per cent,” Ms LaSalle said.

It was not just part-time workers coming out worse off than six months ago, according to the report. The number of suburbs unaffordable for a rental household on an average income of $80,000 increased from 47 to 55.

Suburbs including Prahran, Windsor, Northcote and Ivanhoe moved from moderately unaffordable to unaffordable.

James Barron from Community Sector Banking said many families were forced to move further toward the city’s fringe to afford a rental.

“The downside of that is that it takes them further away from their places of work, childcare centres and other services,” Mr Barron said. “We don’t want to be creating modern day ghettos on the edges of cities; we should be able to provide enough affordable and social housing for low income earners – but we are not.”

Mr Pisarski said it was disappointing that the recent federal budget did not include anything about housing affordability, and though the tax system was not the only thing causing house price growth and rental price increases, it was a place to start.

“Negative gearing needs to be looked at, we think it’s over-generous,” he said. “The capital gains tax discount really does want to be halved at least, to stop the unfair competitive advantage that investors have over would-be first-home owners.”