After a UBS housing report pointed to as many as one in four homes owned offshore by mainland Chinese buyers being kept empty, and a further quarter used on a "temporary" basis, experts have been quick to say the results do not apply to Australian real estate.

Among the naysayers is Jane Lu, head of Australia for Chinese international property site Juwai. She said there was "no hard data" and called the idea of vacant apartments held by offshore buyers as an "urban myth".

"Most Chinese buyers of inner-city apartments are not so wealthy that they can afford to leave their property vacant ??? rather than renting it and earning some sort of income. There are some who do not live there full-time, because it is their second home.

"Chinese investors are no more likely to turn down easy rent money than are Australians ... Australian second-home owners probably have more vacant properties in Ballina and Byron Bay than Chinese investors do in downtown Sydney or Melbourne," she said.

UBS analyst and one of the report's authors Kim Wright said the survey was about Chinese people buying abroad in "all major capital cities around the world" and not just in Australia - but that the trends of how and why they buy abroad is relevant.

Of the 3300 people surveyed for the UBS Evidence Lab: China housing report, released in May, 10 per cent owned residential properties outside of China and Hong Kong - so about 330 people. Of those people, 19 per cent owned property "still under construction".

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And of those 330 people, only just more than 10 per cent owned Sydney real estate, and about half that number owned property in Melbourne - or about 50 people across the two cities.

While it does say a quarter of mainland Chinese buyers of offshore properties surveyed left their property vacant, and a further 25 per cent use them on a "temporary" basis - extrapolating these findings out to make any assumptions about Australia is problematic.

The report itself noted the variations in locations are "not statistically significant" and Ms Wright said "the sample size is too small to draw conclusions down to a specific country level".

SGS Economics' Terry Rawnsley said the UBS report indicated "a very small percentage of Chinese investors are coming to Sydney and Melbourne and a small percentage might be leaving their properties vacant" but that was the extent of what could be determined by the report.

Research released in July by Mr Rawnsley found no significant uptick in the proportion of vacant homes compared with total residential properties in Australia in 2016, compared with historic averages.

Census data shows one million homes are now left empty across Australia - 200,000 more than a decade ago.

"Our analysis of the 2016 census indicated that at most, there would be 70,000 dwellings which could fall into the intentionally vacant category. That is less than one per cent of all dwellings in Australia," he said.

But an analysis of water usage by think tank Prosper Australia from 2015 found 20 per cent of investor-owned properties in Melbourne were sitting vacant, though there wasn't a distinction between local and foreign investors.

And some of those living in inner-city high-rise apartment developments have reported a high proportion of "ghost" properties, which no one lives in.

For many, the decision to hold an empty investment property might actually make financial sense - for instance, those wanting to sell in the near future might achieve a premium for untenanted property.

During the Sydney and Melbourne property booms of the past few years, and a rising number of foreign investment purchases, offshore ownership of Australian real estate has become a hot-button issue.

A survey by University of Sydney academics in May found many Sydneysiders did not believe foreign investors should be allowed to buy Australian property.

Foreign property buyers were recently slugged with vacancy taxes in the 2017 federal budget, an approach which was also taken in Vancouver amid a Canadian property boom in 2016.

Domain Group chief economist Andrew Wilson said it was "likely" foreign investors were a component of what had kept rent prices high and vacancy rates low despite a building boom in Sydney and Melbourne.

"It's hard to get accurate numbers ... the Foreign Investment Review Board numbers are backwards looking and not very specific," he said.