Premier Gladys Berejiklian has been challenged to produce evidence that the government's policies have significantly reduced house prices, after claiming in Parliament that the average Sydney house is $50,000 lower than it would be thanks to state government policies.

Ms Berejiklian said that the record number of housing approvals under her government had stopped Sydney's housing affordability crisis from climbing even further.

"Recently Treasury did some numbers to suggest that because of the rate at which we are approving housing approvals and building and construction, the mean price of an average house in Sydney would have been $50,000 higher if not for our policies," Ms Berejiklian said in Parliament on Wednesday, in response to a question on housing affordability from Newtown's Greens MP Jenny Leong.

The ABS reported this week that there had been more than 75,000 building approvals in NSW in the past 12 months, and 53,000 completions.