Opposition Leader Peter Dutton has announced the Coalition would commit $900 million for an upgrade of the Frankston rail line that the Albanese government scrapped, as he looks to shore up support for the Dunkley byelection.

Mr Dutton, who will visit the seat – which takes in large chunks of Victoria’s Mornington Peninsula – on Friday ahead of the March 2 poll, is hoping to extract political mileage out of Prime Minister Anthony Albanese’s broken promise he would not touch the already legislated stage three tax cuts.