Ms Berejiklian said she would start work on a fast rail network in the next term of government after appointing a British rail expert to consider four potential high-speed routes between Sydney and regional centres.

The four routes the government will ask Andrew McNaughton to consider for faster or high-speed rail are from Sydney north to the Central Coast and Newcastle; west to Lithgow, Bathurst and Parkes via Orange; south to Wollongong and Nowra; and south west to Goulburn and Canberra.

Ms Berejiklian rejected suggestions the pre-election announcement was aimed at marginal seats in the state’s regional areas.

“Far from it. This is a government getting on with what it does well,” she said.

Ms Berejiklian said she could not wait for the federal government or other states to start work on high-speed rail.

“We need to start the work now if we want to see fast rail in NSW. I am not going to wait for the other states and the federal government,” she said.

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 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.