The Morrison government would be forced to abandon $1 billion of water infrastructure projects to pay for water buybacks if NSW quits the Murray Darling Basin Plan.

Deputy Premier John Barilaro on Monday repeated threats first made in August to "walk away" from the plan, having asked for legal advice on leaving the agreement earlier this year.

NSW Deputy Premier John Barilaro. Credit:Joel Carrett

Water ministers will meet in December to discuss the plan, which attempts to balance farming and environmental water use across NSW, Queensland, Victoria and South Australia.

Mr Barilaro and the NSW Water Minister, Melinda Pavey, also are baulking at an agreement to restore another 450 gigalitres to the rivers' health and at projects to help water flowing downstream.