Historic NSW post office sale 'scandalous'

Australia Post's planned sale of Sydney's historic GPO building to foreign buyers is "scandalous" and puts the complex at risk of neglect, the head of the National Trust NSW says.

Singaporean developer Far East Organisation is reportedly in the process of buying part of the Martin Place heritage site for $150 million.

Architect and National Trust NSW branch president Clive Lucas, who specialises in restoring historical buildings, said the building was one of, if not the most, important colonial post offices in the country.

"I think it's scandalous that such an important building in such an important city should be sold off in this way," he told AAP on Thursday.

"A nation that forgets its history is a nation that has no future."

Australia Post says the sale has been cleared by the Foreign Investment Review Board but still has to be signed off by Commonwealth Heritage.

The adjoining Westin Hotel section, sold off by Australia Post in 1997, is already part of Far East's expanding Australian portfolio.

The building, which has become a hospitality hotspot, is heritage listed and the functioning post office will continue to operate under a lease in operation until 2096, according to an Australia Post spokesperson.

The original section of the Sydney GPO - designed by colonial architect James Barnet - opened in 1874 and was the centre of the NSW postage system until 1996, according to the National Archives.

Mr Lucas said he was concerned underfunding of heritage policing would mean the building could be neglected.

However, he questioned whether the Sydney GPO "will ever look like the ones in country towns".

"You can never be sure (neglect won't occur)," he said.

"It's part of the nation's heritage. It should really continue to be owned by Australia."

Far East has invested more than $2 billion in partnerships and acquisitions in prime Australian locations since 2013, according to its website.

"With its attractive urban centres, developed economy, well-regulated business environment and stable market conditions, Australia presents an attractive market for Far East Organisation to build a diversified, balanced real estate portfolio," it says.