The telecommunications workers' union wants a government inquiry into claims of workers being exploited during the ultra fast broadband roll out.
Stories are emerging of workers - hired by firms subcontracted by Chorus service partners -being under-paid and performing tasks they were not trained for.
It followed recent reports that some workers have been unlawfully used as volunteers.
Crown Infrastructure Partners (CIP) has contracted Chorus to build part of the Ultra-fast Broadband Network across New Zealand, the $1.7 billion programme to provide better, faster internet to homes around New Zealand set up by the previous government.
The new Minister for Communications, Clare Curran, said she was aware that CIP had sent a cease and desist letter to all its contractors about inappropriate use of volunteer labour.
Former fibre technician Wilem Brown, 24, quit his $12-an-hour job in August after a year.
He had been told the difference compared to the minimum wage, which was increased to $15.75 an hour in April - would go towards training.
"In the whole year I worked there, I did not ever get any training courses or anything like that. I was just told to 'do it', pretty much," Mr Brown said.
He was employed by a company called Frontier Communications, which was subcontracted by Chorus partner Visionstream, an Australian firm.
Frontier Communications is listed as a wireless communication service, registered in December 2015. One of its two directors had his contract terminated in November 2016.
Mr Brown said he took up the role through Work and Income because he wanted a change after being a passport officer with the Department of Internal Affairs.
He said he assumed he would be trained, but ended up digging up roads and connecting fibre cables to peoples' houses.
"You should be certified to handle certain things, but um, yeah ... I just had to use my wits to get around it.
"That's the thing - I know what to do but I'm not too sure about the certifications I'm supposed to have to do it."
Kay Read, from the Ministry of Social Development, said clients were only referred to employers whose job offers were legitimate and suitable to the individual client, and where the contract terms and conditions met employment legislation.
However, Mr Brown said his employment contract differed from what he actually ended up doing.
He raised his concerns with the employment tribunal, but left the job before there was any formal resolution.
Joe Gallagher of E tū union said workers were being exploited, and tasks were being poorly handled by a delivery model that placed Chorus too far from the coalface.
He said Mr Brown's experience was fairly typical.
"Well, how the set up works is Chorus has awarded the contract to Visionstream as a primary contractor.
"Visionstream runs a dependent contractor model - which means they then go out and look for guys and a van and they essentially set up their own business - then generally what happens, they look for guys to work for them."
Mr Gallagher said the union wanted an inquiry into how the model has been allowed to evolve.
He said it fell short on many fronts, including how use of voluntary labour is interpreted.
A letter sent to all delivery partners in September said volunteering could only be used for observers or trainees, but not in any way that generated economic benefit.
Ms Curran said CIP would support any investigation by the Labour Inspectorate into the alleged practices, which was the right approach.
"The use of voluntary labour in this way is completely unacceptable, and anyone operating a business in this country should be complying with relevant employment laws and standards," she said.
Chorus said it was working hard with all its service companies and their sub-contractors to constantly improve performance. Spokesman Nathan Beaumont said it had made clear that service companies must comply with New Zealand employment law.
"If individuals do have issues with their employment agreements then they should go directly to their employer, but of course, we would be happy to look into any complaints as soon as we're made aware of them, as we did with the use of volunteers in Nelson."
Mr Beaumont said Chorus conceded there was always more to do to ensure the culture was good right across the board.
"Chorus has thousands of people working out in the field rolling out the fibre programme and we are confident this complaint is not reflective of the wider industry.
"However, we are constantly refining our framework for working with our contractors to ensure the best outcomes that we can."
MSD said clients should consider the conditions for employment before accepting a role including appropriate hours of employment, access to childcare facilities, family and religious commitments, required skills, location of the job, and wages.