The population of Sydney is surging faster than predicted, putting more pressure on the city's already-stretched housing and transport needs, new official forecasts show.

Described by Planning Minister Rob Stokes as a "symptom of Sydney's success", figures released by the Government on Monday show the city's population is expected to leap by more than 2.1 million people in the next 20 years - about 170,000 more than predicted only two years ago.

"These are the growing pains of a great global city," said Mr Stokes, who used the release of the updated Department Planning and Environment figures to talk about his ambitions for Sydney's housing market.

When the Department's projections were released in 2014, Sydney was predicted to have a population of 6.25 million within 20 years, up from 4.29 million in 2011. The updated projections anticipate a 6.42 million population in 20 years.