Doug Ford, who made the comments Tuesday on CBC's Metro Morning, said Blair "is the most political police chief we've ever had" and "needs to step down immediately."
It's the latest twist in the scandal surrounding Rob Ford and a video that is in police hands, and is alleged to show him smoking crack cocaine.
The video has yet to be made public.
Reports of the existence of a video first emerged in the spring, with journalists from the Toronto Star and Gawker reporting they had viewed a video of the mayor smoking what appears to be crack cocaine.
That prompted an extensive police investigation of the mayor.
Last week, police charged Rob Ford's friend and occasional driver, Alexander Lisi, also known as Sandro or Alessandro, with extortion. At a news conference last Thursday, Blair confirmed that a tape exists that is “consistent” with what had been described in the media reports.
'Judge, jury and executioner'
Blair also said he's "disappointed" at the contents of the tape, adding they're a "traumatic issue" for the city and its reputation. But Doug Ford says those comments show Blair has overstepped his role as police chief.
"He should not have made those comments," Ford told Metro Morning host Matt Galloway.
"He's created a bias towards the mayor," said Ford, who also said he and his brother support front-line police officers "100 per cent."
"He believes he's the judge, jury and executioner."
On his Sunday radio show, Rob Ford apologized without specifically stating what behaviour he's apologizing for. The mayor also called on Blair to make the tape public.
Meanwhile, many on council, including members of the mayor's own executive committee, say Ford's apology did not go far enough and are calling for him to step down.
Doug Ford's comments suggest a growing rift between the Fords and Blair.
On Monday, it was learned that Rob Ford will not be at Blair's Chief of Police Gala, an annual event that raises money for victims' services and where the mayor is usually a guest at the head table.
Both Ford and event organizers agreed the mayor should not attend the event, given the recent headlines.