The Coalition has launched a senate inquiry into the government's National Broadband Network (NBN) proposal to evaluate its effects on competition, existing services and the need for private investment.

The move comes amid industry criticism that the NBN tender documents are too vague to ensure the network will be open-access and pro-competitive.

Bidders have split between advocates of open wholesale access and others including Telstra which has threatened to withdraw if it is required to resell services at wholesale prices.

Shadow Communications Minister Bruce Billson said the government has struggled to form sound policy from its broadband promises.

"The committee will seek the input of the telecommunications industry - including those excessively gagged under the government's tender process - as well as industry analysts, consumer advocates, broadband users and service providers," Billson said in a statement.

"Openly canvassing the competing interests and evidence-based options for action will ensure that the right public policy settings are identified and understood by broadband service providers and users."

Communications Minister Stephen Conroy dubbed the inquiry an act of "economic vandalism" and said the issues raised by the opposition are addressed in the NBN tender documents.

"It is futile to attempt to make findings on these matters without assessing actual proposals," Conroy said.

"Any regulatory changes will be scrutinised by the parliament [and] the Auditor-General has made it clear that this process may be reviewed following its conclusion.

"During its 11 years in office, the previous government presided over 18 failed broadband plans. The opposition has a shameful and embarrassing record that has left Australia's broadband performance languishing."

The committee is due to report findings in March next year, around the time the delayed NBN contract will be awarded.