Toronto police Chief Bill Blair is threatening legal action against Doug Ford over his claim that a police investigation involving his brother, Mayor Rob Ford, was motivated by revenge against the mayor.

"Doug Ford is lying and I am prepared to take legal action," a Toronto police spokesman quoting Chief Blair told CBC News.

It is the latest missive in an escalating war of words between the Ford brothers and the outgoing police chief.

Doug Ford, an Etobicoke councillor and head of the Rob Ford re-election campaign, made the comments on Friday morning after detectives attempted to serve the mayor a subpoena to appear in court in the extortion case against Sandro Lisi, Ford's friend and former driver. Lisi is suspected of trying to retrieve a video of the mayor smoking crack.

Ford claims that Blair and the police released news of the subpoena to the media before alerting the mayor. He joked that Blair would issue the subpoena through the Toronto Star, which has covered the Ford drug scandal extensively. Ford said Blair "condones this behaviour from his department."

"You wonder why we need a change at the top? This is why we need a change at the top," said Ford, referring to Blair.

Blair applied for his contract as chief to be renewed for a third term, but this week the Police Services Board announced it would not be renewed.

Rob Ford told reporters on Friday that he has not been subpoenaed.

"This is not even news," said Ford of the subpoena. "I've said what I have to say. What you guys are talking about is not news."

Ford said the average taxpayer wants to see savings on city projects on the waterfront, not his subpoena.

Blair will continue as chief until April 2015.

The chief and the Fords have had a contentious relationship since the Project Brazen investigation was made public.

Doug Ford previously accused Blair of taking an inappropriate fishing trip with a member of the Police Services Board. Though Blair was cleared of any wrongdoing in that case, both Fords called on him to resign.

Rob Ford admitted he had "issues" with Blair, a comment that is believed to be about comments Blair made over the mayor's drug use.

Blair had said he was "disappointed" to see the mayor appearing to smoke crack on a video retrieved by police.