LEIGH SALES, PRESENTER: A group seasonal workers from Fiji and Tonga came to Australia with the promise of earning good money to send home to their families. But that's not how things have worked out.

Since they arrived last month under the official program, the fruit and vegetable pickers have been shocked and disappointed. Some of them earn just a few dollars a day after deductions.

As Norman Hermant reports, word of their experience is spreading back to their home islands via an online forum with tens of thousands of members and that could cause dramas for Australian businesses that rely on the flow of seasonal labour.

NORMAN HERMANT, REPORTER: This is how the day begins for the workers that pick the fruit and vegetables that wind up in Australia's supermarkets.

There's barely time for a quick breakfast.

It's not yet 6 am. Pickers from Fiji and other Pacific islands file in for another day in the fields of Northern Victoria.

The workers arrive at this farm as dawn breaks. They will spend the next eight hours or more filling bucket after bucket with tomatoes. Hard work for a decent wage - that's what they signed up for. At the end of the day, that's not what they're getting.

PETERO KANAWABU, SEASONAL WORKER: I thought we come here and do a job and maybe save some money. ... Even my mum cried when I told her my first payslip. I don't know what to do now.

ISIKELI FIFITA, SEASONAL WORKER: This is my pay cheque and this is for the week. I pay after deduction $9.96. I feel sad because there's no money to send to my family in Tonga.

NORMAN HERMANT: These seasonal workers have been shocked by their payslips. Some of them have been staying three to a caravan, charged $120 each per week in rent.

SIA DAVIS, SEASONAL WORKER: And we sharing the same bed as my friend and paying $120 one person.

NORMAN HERMANT: Per week?

SIA DAVIS: Per week.

NORMAN HERMANT: Rent is only one of the deductions that shrinks Sia Davis' payslip. There's also super which she'll get back when she leaves the country, health insurance, daily transport to the farm and back, part of the advance she received to buy bedding and food and tax. At the end of this week her net pay was zero. Her next payslip was the same story: zero net pay for the week.

SIA DAVIS: 'Cause we sweat for that money. And, um, yeah.

NORMAN HERMANT: Others aren't doing much better.

VASITI SAVUNICAVA, SEASONAL WORKER: My first pay cheque, it was only $23.

NORMAN HERMANT: Things are so bad, Vasiti Savunicava's husband has had to wire her money.

VASITI SAVUNICAVA: My hope is for to came here to end much - for me to send money back to my family. Instead of that, they're sending money to me. So they're looking after me again.

NORMAN HERMANT: The workers are here on 416 visas under the Seasonal Worker Programme on contracts signed with AFS Contracting Pty Ltd, based in Shepparton, the heart of Victoria's agricultural food bowl. The company's owner, Tony Yamankol, declined to respond to 7.30's questions about these complaints.

These workers signed their contracts with Mr Yamankol's company through the National Employment Centre run by the Government in Fiji. The contract states they can expect to earn $657 per week before tax and deductions working on the hourly award rate. Alternatively, if they work on the so-called bin or piece rate, it says an average competent worker will earn $595 per week, paid on the number of bins they fill. Then, one final line: "This amount will vary on the number of bins you actually pick."

Merewairita Sovasiga has emerged as the group's advocate.

Do you think your group really understood the contract they were signing back in Fiji?

MEREWAIRITA SOVASIGA, SEASONAL WORKER: Actually, like doing this back home in Fiji, most of the people, even though the National Employment Centre themselves, they were not sure of what was in the contract.

NORMAN HERMANT: The Australian Workers Union says the workers should have been offered a choice and the law requires a separate piece work agreement.

BEN DAVIS, AUSTRALIAN WORKERS UNION: The problem is that there is no negotiation, there is no agreement, which by itself's a breach of the award and more to the point opens up those people to exploitation.

NORMAN HERMANT: After two weeks with little pay after deductions, the Fijians contacted both the Seasonal Worker Programme in the Department of Employment and the Fair Work Ombudsman. The Ombudsman's office told 7.30 it is investigating the workers' complaint.

7.30 understands contractor Tony Yamankol claims the Fijians work slowly and their pay reflects the number of bins they filled. The workers deny this, but after their complaint, Yamankol approached five so-called ring leaders. They recorded him telling them they should leave on their own accord or they'd never work in Australia again.

TONY YAMANKOL, OWNER, APS CONTRACTING PTY LTD (subtitles): I will terminate you. I will cancel your visas. You want to go back on your own will or you want to get terminated? If I terminate you, you will not come back into Australia from any other employer with this program.

NORMAN HERMANT: Merewairita Sovasiga is now staying with Fijian Australians Sakiusa Lesuma. He runs a Facebook forum for Pacific Islanders looking to work on Australian farms and he's been warning the forum's 45,000 members.

SAKIUSA LESUMA, FIJI AUST. & NZ FRUIT PICKERS FORUM: If you tell them to go and work for somebody else in order to gain some money they can send home, the contracts say they can't do it. (Inaudible) the process is flawed from the beginning.

NORMAN HERMANT: About 4,000 Pacific Islanders a year come as seasonal workers and the program's expanding. The Minister for Employment Michaelia Cash told 7.30 that the Government will not tolerate the exploitation of vulnerable foreign workers. The National Farmers Federation is worried about the damage experiences like this one can do.

SARAH MCKINNON, NATIONAL FARMERS FEDERATION: It's very hard to find workers in the first place. And so when you have concerns about how people are being treated on Australian farms circulating in the media, on social media, that makes it even harder for all of the good, hard-working, decent farmers to find the workers they need.

NORMAN HERMANT: Of the 20 Fijians who arrived to work for AFS in January, 13 have now quit and left the caravan park. They have three months left on their seasonal worker visas.

SIA DAVIS: But for me, I was - I wish I was back home. I would never come, you know? I didn't thought that it would be like this.

NORMAN HERMANT: Most of these Fijians just want their time as seasonal workers in Australia to be over.

LEIGH SALES: Norman Hermant with report.