More than 100 plasterers have stopped work at the Royal Hobart Hospital construction site after questions were raised about their qualifications, visas and wages.

The CFMEU's Kevin Harkins said 120 of the workers were Chinese visa holders employed by Melbourne company Accuracy Interiors.

He said they had not been paid for six to eight weeks.

"We found out that they hadn't been paid for a number of weeks, so yesterday we intervened in the matter to make sure people get paid money and get paid properly," he said.

"We're questioning whether the visas they've got are correct, we're questioning whether their wage rates are correct and all the matters that are connected with their employment."

Mr Harkins said the foreman in charge of the workers was sent off the site this morning, and that some could be owed up to $12,000.

CFMEU organiser Kevin Harkins says the workers haven't been paid for weeks. ( ABC News: Ellen Coulter )

Mr Harkins said about 40 Tasmanian plasterers, employed by the same company, remained on the job.

"It will obviously mean quite a few delays, the locally based employees — who are all paid correctly under a union enterprise agreement — are continuing to work, but the Chinese workers have stopped work until the mess is sorted out," he said.

A worker who spoke to the ABC but did not want to be identified said the lack of payment was causing problems for him.

"We are here six week but no money," he said.

"A lot of people … borrow the money and buy the food. Very sad."

It is unclear how long the Chinese visa holders will be off work, which could cause delays for the $689 million redevelopment.

"The Victorian-based workers may well up and leave and then we've got an issue with not having enough people here to do the work," Mr Harkins said.

"Once it's resolved obviously they will have an opportunity to go back to work, but it could be a day, it could be a week, it could a month."

A spokeswoman from John Holland-Fairbrother — the construction companies in charge of the Royal Hobart Hospital re-development — released a statement:

"We understand there is an issue between one of our subcontractors and their workforce at our Royal Hobart Hospital site. "It is important that everyone who works on a John Holland project is treated fairly and in line with their entitlements. "We expect our subcontractors to fulfil their obligations to their employees and we are currently trying to verify the concerns raised."

Accuracy Interiors has been contacted for comment.

Hospital revamp manager seeks answers

Ben Moloney, project director for the RHH redevelopment, said he had directed John Holland-Fairbrother to assess and report back on the concerns around pay, visas and qualifications, which were first brought to his attention on Thursday morning.

Ben Moloney says there may be further audits of the redevelopment. ( ABC News: Ellen Coulter )

"And we'll be further looking at options as to whether or not to undertake further audits ourselves in addition to the investigation being undertaken by the managing contractor," Mr Moloney said.

He said K-Block was still on track for completion by the middle of 2019.

Premier Will Hodgman said he had not been briefed on the situation but it would be investigated.

"I think we need to understand the facts and make proper investigations and inquiries to that and ensure that people working on the project are being appropriately employed and that the project is proceeding as it should," he said.

"I have very firm expectations that the project be delivered on time and on budget. It is absolutely critical for our state's health system and a lot's invested in it, and we expect it to be done."

Most of the plasterers on the hospital redevelopment are overseas workers on visas. ( ABC News )

Labor spokesman David O'Byrne said the issue was one of many for the project.

"We're hearing stories of cash in hand $15 an hour, we're hearing a whole range of accusations around wages and conditions on the Royal Hobart site," he said.

"How could the Government not know on their watch that this was occurring?"

Mr Harkins said he understood the workers were also finding it hard to secure long-term accommodation.

"They've been staying in rented houses and those rented houses appear to be no longer available, so that's another issue we will have to look at to try and resolve," he said.

Tasmania has been experiencing a rental crisis, with a housing boom in recent months.