The first set of tracks have been laid for Sydney's $2.1 billion light rail project, marking a major milestone for construction of the line from the CBD to Randwick and Kensington in the south-east.

Premier Mike Baird and Transport Minister Andrew Constance helped pour concrete to cement in place a 60-metre section of track on Anzac Parade in Kensington on Friday – 55 years after the final tracks that made up Sydney's old tramway network were ripped up.

While residents critical of the project have questioned the forecast capacity of the new line, Mr Constance described it as a congestion-buster capable of moving up to 13,000 passengers in both directions between 7am and 7pm.

"We all know congestion is getting worse in Sydney and, with daily trips to the city centre expected to increase by almost 25 per cent by 2031, this will help bust congestion," he said.