The Baird government has left the way open to consider a congestion tax on motorists wanting to drive into Sydney's CBD once major transport projects are completed.

"There is nothing ruling out future governments considering it once the city is settled," Transport Minister Andrew Constance told investors at an investment banking conference last week when asked whether a congestion charge could be introduced to prevent gridlock in the city.

However, Mr Constance insisted that the government had no plans on the table for a congestion tax, and wanted large projects such as the $2.1 billion CBD light rail line finished before considering road-user charges. Construction of tram lines from Circular Quay to Randwick and Kensington in the city's east are expected to take more than three years.

"I am a bit reluctant on congestion charging in the city given what we are doing to force people's change in behaviour with a construction zone down the main arterial road into the city," he said.