Tech billionaire Elon Musk’s pitch to tunnel through the Blue Mountains could be “problematic” for its World Heritage status with the United Nations, a conservation group says.

The Tesla CEO floated tunnelling 50 kilometres through the UNESCO listed World Heritage asset for about $1 billion, in response to a tweet from ex-Greens NSW MP Jeremy Buckingham.

“The National Trust applauds all innovative thinking when it comes to transport options that connect communities with reduced impact on the environment,” NSW CEO Debbie Mills said in a statement to The New Daily.

“A great opportunity for this kind of thinking would be a fast train connection from Sydney to Newcastle. But tunnelling through the Blue Mountains World Heritage would be problematic.”

Motorists wouldn’t drive their vehicles through the tunnel to Lithgow, connecting to the central-west. Cars would be secured to electric platforms that transport them between stations at high speed.

Mr Buckingham – who left the Greens following unproven allegations of sexual misconduct and intimidation, which he denies – said the area is already impacted by infrastructure and argued underground tunnelling and the electric vehicles would be less harmful than expanding existing highways.

Transport for NSW said while the department welcomed bold ideas, “a high-level analysis of costings reveal that Mr Musk’s project could not be delivered for his proposed price”.

“Key issues that do not appear to be considered in Mr Musk’s proposed tunnel (which have been factored into our cost estimates) include ventilation and emergency egress,” a spokesperson said.

“Other key issues include geotechnical conditions and integration with the wider transport network (given this appears to be a fully independent / bespoke transport mode).”

The state government also wants to connect to Lithgow and out to Orange, and is studying a statewide fast rail plan with $4.6 million.

Mr Buckingham said he believes Mr Musk is “very serious” and disagreed the $1 billion quote was unachievable, saying the entrepreneur had always proved people wrong.

In 2017, Mr Musk made good on his Twitter promise to deliver the world’s largest lithium-ion battery to South Australia within 100 days.

Their only interaction on the proposal has been a Twitter exchange.

About $15M/km for a two way high speed transit, so probably around $750M plus maybe $50M/station

— Elon Musk (@elonmusk) January 16, 2019

Mr Musk’s The Boring Company is testing a similar two-kilometre tunnel in Los Angeles and planning another for Chicago.

James Whitten, a PhD Candidate in Urban and Regional Planning at the University of Melbourne, said Mr Musk’s tweet did not seem to be a “meaningful debate about the real transport needs of regional communities”.

He said the actual cost of the tunnel would likely outweigh the benefits and there are probably more viable options to connect to the regions.

NSW Farmers Association welcomed the proposal, saying transport added 30 to 40 per cent of the cost to agricultural production.

“One of the biggest challenges to growing the state’s food economy is the inadequate east-west transport connections between the food bowl that is western NSW and Sydney,” president James Jackson said in a statement.

Potential route. pic.twitter.com/AjH1O4QAby

— Jeremy Buckingham (@BuckinghamJN) January 16, 2019

Mr Buckingham called on the government and Labor opposition to meet with Mr Musk.

“Autonomous, electric vehicles that generate zero pollution are the future of transport. It would be madness not to further investigate what could be an infrastructure and planning game changer for Sydney and our regions,” he said in a statement.

“You could live out in the beautiful western region of NSW, enjoy the lifestyle, clean air and national parks while commuting into jobs centres of Penrith and western Sydney. The infrastructure plan takes the pressure off traffic congestion and resources in Sydney, while providing a lifeline for our regions.”

UNESCO has previously heard concerns about the planned Badgerys Creek airport, but was advised it would have low impact on the heritage value of the Blue Mountains.

The International Council on Monuments and Sites (ICOMOS) also warned the NSW and federal environment ministers that the proposal to raise the Warragamba Dam wall 14 metres would breach obligations to protect the heritage of the Blue Mountains.

Mr Musk was heavily criticised and eventually apologised last year after calling one of the Thai cave rescue divers a “pedo”.