The government's National Broadband Network (NBN) gag policy will be enforced on bidders responding to a new opposition call for industry submissions on the financial and regulatory environment of the future proposed network.

The coalition launched a senate inquiry into the NBN process to evaluate its effects on competition, existing services and the need for private investment.

Shadow communications minister Bruce Billson promised bidders legal immunity to facilitate frank discussion on the tender process, but submitters will still not be able to speak about NBN proposals.

The senate committee will pursue industry members, bidders and analysts to garner opinion on the controversial NBN process, including the relevance of structural or functional separation in both a public-private funded network, as mandated by the tender documents, or similar to Telstra's proposal which would be built entirely from private funds.

A spokesperson for Billson's office said the committee has provided parliamentary privilege for bidders against legal action, but it will be up to the government to reprimand contenders for discussing NBN proposals.

"We want discussion to be frank and open so they have the immunity to do so, but under the RFP it is up to the Minister to preclude [submitters] from being accepted as a bidder," the spokesperson said.

"It would be pretty unreasonable for the Minister to hold it against bidders who come forward to give evidence."

Optus will place a submission with the committee, similar to the government's own call for submissions, regarding "competition and consumer welfare with a focus on the need for general open access".

A spokesperson for the telco Optus could not confirm whether this would include debate over the need for the NBN builder to be structurally or functionally separated.