Finance Minister Mathias Cormann and Communications Minister Mitch Fifield announced Mr Clarke, who led the Communications Department from 2013 to 2015, had been appointed to the board for a three-year term from August 22.

He moved to Parliament House when Mr Turnbull toppled former prime minister Tony Abbott in September 2015, retiring from the Prime Minister's office in April and handing over to Greg Moriarty.

Mr Moriarty was named Defence Department secretary last month, handing the chief of staff role to respected former diplomat Peter Woolcott.

The government said Mr Clarke's extensive experience at senior levels across government would benefit the NBN Co board.

While Mr Turnbull's departmental secretary, Mr Clarke oversaw the large scale review and reform of the National Broadband Network project and developed an in-depth understanding of the telecommunications market.

He was previously Resources, Energy and Tourism Department secretary from 2010 to 2013.

"Mr Clarke is uniquely placed to assist the nbn Board as the rollout increases in scale and the company transitions from network construction to an operational business," Senator Cormann said in a statement.

"Mr Clarke's extensive government and regulatory experience will enhance the board's capability through to the completion of the NBN rollout in 2020."

On Tuesday, NBN Co said it had more than doubled full-year revenue as more homes and businesses connect to the government-owned network.

NBN Co said its revenue for the 12 months to June 30 increased to $1 billion, up from $421 million a year earlier.

Currently 2.4 million homes and businesses receive NBN service, up from 1.1 million. A further 5.7 million premises are ready to be connected.

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