The 47-year-old Liberal moderate will made the announcement on Sunday afternoon.

He will resign as Transport and Roads Minister this week, and as the Member for Bega by the end of the year.

Prime Minister Scott Morrison has welcomed the move.

"I warmly welcome Andrew Constance's decision to seek endorsement to be part of our federal Liberal team as our Liberal Candidate for Gilmore.

"Andrew has an outstanding local reputation and a great deal to offer at the federal level, especially given his experience in the NSW Government. He tells it straight and would make a great member of our team," the Prime Minister said.

The move confirms he will not run for the NSW Liberal leadership in the wake of Gladys Berejiklian's sensational resignation on Friday due to an investigation by the corruption watchdog ICAC.

"Like so many of us, I am heartbroken for my long-time friend Gladys Berejiklian. By retiring from State Cabinet and NSW Parliament, I will provide an incoming leader the opportunity to fill this position," he said in a statement.

He gave his ongoing support for Ms Berejiklian.

"Gladys is one of the best Premiers we have ever seen. I hope she bounces back as strongly as possible, because I know we have not seen the end of her yet," the statement read.

Mr Constance said he would continue to serve his South Coast community while the party sought new direction at a state level.

"I will continue representing my community on key local issues, such as the new hospital developments, and ensuring the community is listened to on vital projects such as the Milton Ulladulla and Moruya Bypasses," the statement read.

NSW Treasurer Dominic Perrottet is expected to announce later on Sunday that he will run against Planning Minister Rob Stokes for the top state job. Mr Perrottet has been endorsed by former Liberal Prime Minister John Howard.

Mr Constance, who has previously held the portfolios of industrial relations, finance, disability and ageing, has been seeking a path to Federal Parliament for several years. He pulled out of the race for Eden-Monaro in 2020 after John Barilaro, his state colleague and NSW Nationals leader, denigrated him in a front page news story.

Currently held by Labor's Fiona Phillips on a margin of 2.6 per cent, Gilmore covers the Shoalhaven and South Coast town centres of Nowra-Bomaderry, Kiama, Milton-Ulladulla and the area around Batemans Bay.

The seat was contested by the Liberal Party in 2019 by Warren Mundine, who had joined the party on the same day as announcing his run.

The seat was also contested in 2019 by the Nationals by former NSW Minister Katrina Hodgkinson.

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