THE National Broadband Network’s delivery time has already blown out to 2020 — now new analysis shows its cost to the budget bottom line could soar to as much as $2.1 billion a year over the next decade.

To date, the network has lost $8.3 billion of the $20.3 billion allocated by the Federal Government, The Australian reported today.

But that won’t appear in the budget update on Monday.

The project is not in the papers, and hasn’t been since the Rudd Government launched it, because it was intended to eventually deliver a return.

New estimates from the Parliamentary Budget Office, however, show the expected interest costs from the Government borrowing to finance the project could impact the budget.

The PBO estimates the amount the government will borrow to fund the $49 billion project to give Australians faster internet will rise from $20.3 billion to its final level of $29.5 billion this year.

Then — if interest rates rise from 2.5 per cent to 5.5 per cent in 2026 — the interest cost of borrowing this amount will reportedly rise from $580 million this year to $2.1 billion in a decade.

The office says the final impact on the budget will not be known until the NBN is privatised and the market places a value on it.

If the sale price is less than the total cost to finance it, the budget bottom line will take a hit.

The office estimates the NBN has so far reduced the government’s net worth by $8.8 billion.

This takes into account asset revaluations and the impact of interest payments on the government’s debt, given the project has made $8.3 billion in losses while being rolled out.

Finance Minister Mathias Cormann said the project would have a large upfront investment and operating losses in the first years, before it began to generate a positive cash flow and an operating profit.

Earlier this week, Shadow communications spokeswoman Michelle Rowland criticised Prime Minister Malcolm Turnbull for failing to meet his 2013 election promise that all Australians would have the NBN by 2016.

The completion date has been pushed back to 2020 for some time but the Opposition seized on the promise, with just days left to go before the end of the year.

Communications Minister Mitch Fifield hit back, sating the Coalition had made more progress than Labor when it was in government.

“In less than three years, the Coalition has dramatically sped up the NBN rollout, which is connecting close to 100,000 Australian households and businesses to better broadband every single month,” he said.

“This is exactly what we said we would do when we came to Government in 2013.”

To date, 1,570,721 premises nationally have activated the NBN, representing less than half of the 3.5 million premises that are NBN ready.