But transport experts say the enormous cost of faster rail or high-speed lines makes it unachievable without a national approach. A new line for high-speed trains from Sydney to Newcastle is estimated at upwards of $40 billion given much of it would have to in tunnels.

While the announcement was scant on detail,Ms Berejiklian said it could involve upgrading existing rail corridors,extending them or build entirely new rail lines.

"I can give you this assurance:we will be starting in the next term of government. It might take us many years to get us to the network we want to build,"she said.

But NSW Labor leader Michael Daley said the state's Liberals had struggled to build a light rail line between Sydney's CBD and the south east yet"they want us to believe that they can do a fast rail network in the next term of government".

"[It is] absolute pie in the sky stuff from a desperate government in panic mode,"he said.

The latest announcement comes five months after NSW Labor promised to commit funding fora study into reducing the four-hour train journey time on the existing rail line between Sydney and Canberra if it is elected to government at the election next March.

The Berejiklian government will direct $4.6 million from funds received from the sale of the Snowy Hydro scheme towards the initial planning for high speed rail.

Professor McNaughton,who has been involved in the United Kingdom's High Speed 2 rail project costing nearly $100 billion,said NSW's topography was not"exactly ideal for very high speed"rail,and it was important to remember that fast rail was expensive and"very fast rail is very expensive".

"It's not about speed,it's about time. I am usually asked how fast is fast and the answer is as fast as necessary to ... get the choices we want,"he said.

"If you make it the Concorde for the rich you've defeated the whole purpose of doing it. If this is not a system that everybody can use I wouldn't be here."

He will chair the state panel charged with delivering plans to the government by Christmas next year.