The battle between the mayor and a prominent Calgary developer took a nasty turn on Friday as homebuilder Cal Wenzel sued Mayor Naheed Nenshi for $6 million.

Wenzel, the CEO of Shane Homes, claims the mayor defamed him for political gain, citing a radio interview in which Nenshi compared the development mogul to Don Vito Corleone, Marlon Brando's mafia boss character in the Godfather movies.

Cal Wenzel and the mayor clashed after a video emerged in April of 2013 in which Wenzel urged his fellow developers to vote for pro-business candidates in Calgary’s municipal election.

Wenzel has made no secret of his desire for more pro-development voices on city council and, in that leaked tape recorded in 2012, Wenzel implied three councillors were already "taken care of".

Two city councillors confirmed they received donations from Shane Homes but insist the donations did not affect their votes in council.

Friday's lawsuit claims the mayor distorted Wenzel's recorded comments, then tried to smear the developer as a re-election strategy.

Nenshi is presently out of town and has not been formally served with legal papers. The mayor will not respond to the allegations until he is made fully aware of what the lawsuit entails.

With files from CTV's Bill Macfarlane