Turnbull denies gagging NBN contractor

Federal communications minister Malcolm Turnbull has denied gagging the company rolling out the National Broadband Network in Tasmania from speaking to a Senate inquiry.

Labor senator Stephen Conroy has accused Mr Turnbull of preventing contractor Visionstream from addressing the Senate committee looking into the NBN.

Former minister Stephen Conroy says contractor Visionstream was invited to speak in-camera to the committee but declined because of its contract with NBN Co.

"What we're seeing is an increased level of secrecy from Mr Turnbull," Senator Conroy told reporters in Hobart, where a committee hearing was taking place on Tuesday.

"Malcolm Turnbull can release Visionstream from that contractual promise."

Tasmania was to be among the first areas in the country to have the super-fast broadband rolled out.

The project stalled last year after contractual issues and asbestos problems.

Senator Conroy said Visionstream could answer crucial questions about progress in the island state.

But Mr Turnbull rejected the suggestion he had attempted to gag the company.

"At no stage has NBN Co sought to prevent Visionstream from appearing before today's Senate committee hearings," a spokesman for Mr Turnbull said.

The spokesman said the rollout had recommenced before Christmas, blaming the previous Labor government for stoppages.

"Work on the NBN rollout in Tasmania is back on track," he said.

Labor says 60,000 of the 200,000 homes promised fibre to the home in Tasmania could now miss out on the technology.

Senator Conroy said contractors who had invested millions on the promise of four to five years' work faced uncertainty.

"All the contractors are asking, all the business groups are asking, is please keep your promise," he said.

Mr Turnbull's spokesman said 33,000 premises had been given access to fibre in Tasmania, with contract instructions issued for another 17,000.

He said NBN Co would enter contracts in coming months for another 19,000 premises.