The state government has defended the independence of the consulting firm whose sums were the basis for its controversial push to slash Sydney councils.

Accounting and consulting giant KPMG, whose figures have been used to justify the government's controversial merger policies, donated about $100,000 to the NSW Liberal Party shortly before the elections that brought the Coalition to power in 2011.

The firm was also paid about $870,000 to audit Liberal Party accounts in 2015.

"How can you claim KPMG's report on your forced council mergers is independent," asked the opposition spokesman on Planning and Infrastructure, Michael Daley, in question time in the NSW Parliament on Thursday.