After working 13-hour shifts in stifling conditions, some of the volunteers at the Melbourne Fashion Festival in March were on the verge of collapse.

Tough conditions for volunteers at Melbourne's marquee fashion event are laid bare in dozens of leaked feedback reports obtained by Fairfax Media. Some of the volunteers say they went without food and water.

The documents point to the ugly underbelly of Australian fashion – the working reality beyond the glamour of the runway.

They highlight a growing problem of exploitation of unpaid interns and volunteers, people trying to get a break in competitive industries such as fashion and the media.

Tammy Walters is one of them. A fashion lover, she has volunteered at the past three fashion festivals. This year, she says, conditions deteriorated.

Working backstage without airconditioning on a searingly hot day, temperatures soared as models rushed to change outfits, and clothes were steam-pressed.

"A few girls had to sit down because they were about to faint," Ms Walters says.

As for food, she says festival staff were heard to quip there was no need for it. "You're in the fashion industry."

Her experience was not unique.

The documents show volunteers being required to work 12 to 13-hour shifts, often without breaks, finishing at 10.30pm or later.

Volunteers were not allowed to bring their own water, they say, because it would have interfered with the festival's water sponsorship deal.

Some complain of physical distress from constant "unsafe" heavy lifting. Others describe "rude" supervisors who yelled at and demeaned volunteers.

Many say they were too "scared" to complain, particularly as they wanted to continue in the industry.

At least one volunteer alleged in the feedback documents that, when they complained about a lack of food breaks, a paid member of staff was heard to say: "F--k them. Most of them are fat anyway".

In a statement, the festival said it took feedback "very seriously" and "does not encourage or expect that any volunteers do anything they are not comfortable with and provides access to catering and beverages", including water "at all times".

This was disputed by numerous volunteers.

The festival stressed it had a process to deal with health and safety issues.

"All lodged reports and any feedback received post the festival provide important intelligence to make changes and further improve the program and experience for volunteers in the future."

The Melbourne Fashion Festival Ltd is run as a not-for-profit but is closely tied to the wider fashion industry.

Its objectives are commercial, including stimulating retail spending, promoting global branding and tourism, and influencing consumer sentiment.  Major backers include Virgin Australia, the state government, David Jones, Fiat, Tiffany & Co, Crown and NAB.

It generated $6 million in revenue in the 2014-15 financial year, saving hundreds of thousands of dollars a year through its use of about 400 volunteers.

Growing employer reliance on unpaid interns adds to concerns about declining conditions and underpayment in Australia, including the spread of "black jobs" for temporary foreign and other vulnerable workers.

Many volunteers at the festival are students wanting experience or a break in a tough industry where lengthy periods doing unpaid work is common.

The complaints have even led the company that supplies the volunteers to declare that the festival failed its unpaid helpers.

Alex Rixon-Booth, the director of I Need Helpers, said the festival had ignored his recommendations about managing volunteers.

"It was extremely disappointing to witness how volunteers were treated,"he said.

"We don't agree with the decisions to have volunteers working excessive hours and being mistreated like they were".

Fairfax Media has spoken to several volunteers who confirmed the poor working conditions.

"Some of the staff were not very nice to us," said one fashion student. "It was quite unfortunate, a lot of us were looking forward to [the festival]. That kind of treatment put us off and we didn't go back."

The leaked documents also point to other problems.

These include copies of job descriptions asking for "interns" to work for five months up to five days a week, unpaid. Many of the positions required advanced technical skills. Such unpaid positions could fall foul of the Fair Work Act.

The festival did not deny the job advertisements but said it did not engage interns in 2016.

Similar events overseas, notably the London Fashion Week, have been hit by protests over non-payment of interns.

There is little research on the extent of employer reliance on interns or volunteers in Australia.

But a 2013 report by the University of Adelaide for the Fair Work Ombudsman, noted troubling signs, since the global financial crisis, of unpaid work replacing paid jobs.

Co-author Professor Andrew Stewart told Fairfax Media that volunteering was generally acceptable if its primary intention was to help someone else or a good cause – a church, a sporting club or political party.

He said on the "face of it", volunteers at fashion week were a different category.

"It's a commercial enterprise; the goal here is still making money," he said.

If you are doing productive work, you should at least receive the minimum wage, he said.

Professor Stewart said there was a risk of a culture of unpaid work taking root, where a few days' unpaid work turned into a week and then into months.

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