Liberal MP Scott Buchholz charged taxpayers more than $1700 to cruise Sydney Harbour with his partner aboard a luxury vessel chartered by mining magnate Gina Rinehart.

Mr Buchholz, the assistant minister for roads and transport, was a guest of Ms Rinehart at the National Agriculture and Related Industries Day Gala Dinner on November 21.

The Starship Sydney, scene of the 2018 National Agriculture & Related Industries Day Gala Dinner attended by MP Scott Buchholz. Credit:Alex Healing/Andrew Meares

The cocktail function was held on board the palatial Starship Sydney, billed as the largest glass cruising vessel on the harbour, which seats 350 guests for a sit-down black-tie dinner.

Agriculture Minister David Littleproud also billed taxpayers to attend the function, where he delivered a keynote speech.