The NSW Liberal Party sent an email in Premier Mike Baird's name soliciting a donation from a banned donor - a Sydney property developer - in an embarrassing blunder shortly before Saturday's state election.

The error comes despite the party effectively ending the careers of a succession of Liberal MPs last year over accepting money from property developers, who have been banned from donating to NSW election campaigns since 2010.

NSW Premier Mike Baird. Credit:James Brickwood

NSW Liberal state director Tony Nutt emailed Mosman developer Peter Maccormick on March 18 requesting that he "show your support" by donating to the party.

The request was sent to Mr Maccormick's Napier Properties email address before being followed up with an email in Mr Baird's name last Thursday.