Sydney Trains could soon be privatised as the NSW government considers the option of selling the transport network as part of a cost recovery plan.

Confidential documents obtained by 9NEWS reveal that the "cost recovery of public transport" will be the focus of a looming reform, and one approach being considered is the privatisation of Sydney Trains.

The train network carries almost 300 million people each year, and has been Sydney’s primary public transport network since 1855.

Now the Baird Government is being urged to put it up for sale.

Advice to Treasurer Gladys Berejiklian said there was an urgent need for "greater competition” for “service delivery".

Shadow treasurer Michael Daley said the move would mean more expensive public transport.

“If Mike Baird sells their train network, (the public) will pay much higher fares for a much worse service,” he said.

Liberal MPs believe the sale would only relate to the operation of the trains, with the tracks, trains and stations remaining in Government hands.

Transport Minister Andrew Constance said past successes with privatisation would influence the government’s decision.

“We have had some success in the past with the ferries,” he said.

“I’m not going to rule anything in or out into the future but the point I would make is there is no proposal before the government.”

The move would follow the privatisation of Sydney’s electricity network, Newcastle’s light rail, bus and ferries, and the new metro train.