The company responsible for the rollout of the NBN in Tasmania has denied a dispute with a "small number" of contractors will slow down construction work.

Six frustrated contractors met with Visionstream yesterday afternoon in what was described as a "crisis meeting".

Unions Tasmania boss Kevin Harkins said the discussions led to Visionstream agreeing to seek more money from NBN Co to pay contractors for the next stage of the rollout.

"Visionstream are trotting off to talk to NBN trying to renegotiate their contract position," Mr Harkins said.

"There's an election coming up, Visionstream might be playing silly buggers."

The Examiner understands that Visionstream had underestimated the cost per connection and cannot afford to pay contractors at the rates they are quoting for future work.

Civil Contractors Federation chief executive Tony Cook said contractors had agreed to finish what they were working on, but uncertainty surrounds the next stage of the project.

Contractors were asked to sign a confidentiality agreement covering the content of the meeting.

Visionstream spokeswoman Louisa Graham downplayed yesterday's meeting as a "normal meeting" to discuss work schedules and commercial negotiations for planned works, including moving some contractors off day rates.

"That means if a subcontractor does half a day's work on an NBN site, we pay them for the work that's been done, no more, no less. It means we're not paying a full day's rate for half a day's work."

Ms Graham said there were plenty of contractors willing to carry out the necessary construction work and it was up to individual contractors to decide if they wanted to be part of it.

However, Ms Graham later admitted the extended temporary halt on asbestos remediation had stalled work.

"The real current issue in Tasmania is about volume of work. At the moment, due to the extended temporary halt on asbestos remediation works, we have limited work available, however, we are actively bringing two new worksites to construction."

Federal Bass Liberal candidate Andrew Nikolic said contractors had been misled by Visionstream about the extent of work that would be generated by the NBN.