"There is nothing new about these payments nor can they be described as having been 'brought forward'," he said.

Turnbull also said that the NBN price tag had risen by as much as $400 million. He said this was evident in the government's broadband spending which is forecast to hit $484 million in the 2012-13 Department of Broadband, Communications and the Digital Economy (DBCDE) portfolio budget compared to $57 million in the 2011-12 DBCDE portfolio budget.

"The sum Australian taxpayers are being forced to invest in the NBN between July 2011 and June 2014 has apparently blown out by $400 million, even though the NBN is at least a year behind schedule in its rollout," Turnbull said.

"Yet the network only has 5000 or so customers currently using its fibre network, compared to the 137,000 projected by June 2012 in NBN Co's corporate plan."

Follow Hamish Barwick on Twitter: @HamishBarwick