Malcolm Turnbull’s intervention in a fight over the future of Craig Kelly has sparked a war inside the NSW Liberal Party's dominant moderate wing, with its leadership accused of capitulating to conservatives.

A blistering email obtained by the Sydney Morning Herald and The Age reveals the decision by factional leaders Trent Zimmerman and Matt Kean to support Prime Minister Scott Morrison's plan to rescue Mr Kelly from certain preselection defeat has triggered bitter recriminations.

In a late-night missive on Monday, Sally Betts — a close ally of the former prime minister — attacked Mr Zimmerman and Mr Kean for helping save Mr Kelly, a conservative backbencher who helped bring down the National Energy Guarantee and Mr Turnbull's leadership.

"To say that the moderates are disappointed in you, as our supposed leader, is an understatement," she wrote to the North Sydney MP.