The cost of acquiring properties for the second stage of the Sydney Metro rail line is expected to hit $1.8 billion, with less than one-quarter of 187 anticipated transactions completed to date.

It means the NSW government is expected to spend more than $3.3 billion on property acquisitions for the Sydney Metro City and Southwest and the WestConnex motorway.

The opposition said the numbers highlight the government's failure to release a landmark report, delivered more than two years ago, by David Russell, SC, on how to make the compulsory acquisition system fairer.

The figures, obtained by Labor under access to government information laws, reveal 39 "freehold acquisitions" had been completed for the Sydney Metro City and Southwest by September 1.