The number of Australians with at least five rental properties has increased by more than 6%, according to new figures from the Australian Taxation Office (ATO). The new figures shed light on the nation’s investment-led property boom which regulators are rushing to contain

After Andrew Thorburn, group chief executive officer of NAB, last week singled out tax concessions as one of the main drivers of the housing boom, ATO statistics subsequently revealed that individuals with interests in five or more rental properties jumped 6.3% to 37,213 in 2014-2015.

More than 19,198 people had interests in six or more rental properties, while 118,412 people had interests in three. “It seems that once you’re hooked on the drug of investing in property, you want more and more,” said Brendan Rynne, chief economist at KPMG.

In contrast, the number of taxpayers negatively gearing by claiming a net rental loss declined 1.8% to 1.28 million. Rental losses fell 2.3% to $11.1bn due to declining borrowing costs as the RBA’s official cash rate fell 0.5 percentage points.

While nearly 75% of the 2 million people with rentals had just one investment, Labor was quick to swoop onto the figures, saying they were indicative of the “excesses” of negative gearing, which allows investors to lower their taxable income by claiming rental losses.

A spokesperson for the Property Council of Australia argued that people with six or more investments constituted a very small percentage (0.009%) of property owners. The council added that 807,521 users of negative gearing had taxable incomes below $80,000 annually. However, Labor said using taxable incomes was “meaningless” because it was after deductions such as negative gearing.

According to the Grattan Institute, a non-partisan think tank, Australia’s higher-earning professionals (such as surgeons and lawyers) received a greater average tax benefit from negative gearing than lower-earning professionals (such as nurses, teachers, and sales assistants). 

At the more extreme end of the spectrum, Grattan’s data indicated that 46 people had total incomes of more than $1m, but taxable income of $6,000 or less. Of the 46, eight claimed rental losses. 

Tax concessions have become increasingly topical as the five-year property boom in the southeastern capitals has pushed house prices out of reach for many residents. Exorbitant house prices are also worrying regulators who’re concerned about record-high household debt, stagnant income growth, and lax bank lending standards.