McCririck will not be part of the IMG-produced Channel 4 Racing coverage when it relaunches in January 2013.
Derek Thompson, Mike Cattermole and Alastair Down have also been dropped, although veteran form expert Jim McGrath will stay on the team as an analyst.
Former Celebrity Big Brother contestant McCririck has a broadcasting style that is not to some people's tastes, but he is widely regarded as being among the most high-profile horse racing presenters.
But instead, Channel 4 have opted for Clare Balding to lead its new-look coverage, which has been expanded to include a range of events poached from the BBC, including the Grand National.
Speaking to The Guardian, McCririck said that he was being "sacked" by Channel 4 "after audience research".
"Yet, as Clare Balding, a terrific choice to lead the new young team, said recently, I've become the face of racing alongside Frankie Dettori and now of course Clare herself."
The 72-year-old said that he was "so sad" that "ageism" had allegedly guided Channel 4 in creating the new presenting team.
He added: "Among the 13 slated to be on screen, only Jimbo McGrath is over 50."
McCririck also expressed his frustration at only being contacted by Channel 4 shortly before the racing lineup was revealed on Thursday afternoon (October 25).
"Without any consultation or being asked to change my presentation style, I was only told by Channel 4's head of sport, Jamie Aitchison, half an hour before their press release," he said.
"Racing continues to prosper and is a magnificent sport for all ages and classes of society. I trust those now in power, having shown their macho images as all new producers do by getting rid of their most well-known older performer, don't forget that racing appeals to all generations."
A Channel 4 spokeswoman denied McCririck's accusations of ageism and said that the presenters were selected in line with "a change of tone and style" to the programme.
"It hasn't been an easy process and there have been complications on the way but, with regards to the choice of the squad, we were conscious that the programme will have a very different feel," she said.
"Behind Clare Balding as lead presenter and Nick Luck in a supporting role, we were looking for a more journalistic approach to the content."
From 2013, Channel 4 Racing will be the new home of horse racing on TV. It will broadcast 88 days of coverage a year and show nearly 300 hours of live action.
This includes a range of premium events, including the Cheltenham Festival, Aintree's three-day John Smith's Grand National meeting, the Investec Derby Festival from Epsom Downs, Royal Ascot and Glorious Goodwood.
Last year, former Countryfile presenter Miriam O'Reilly won a landmark industrial tribunal verdict against the BBC, after accusing the corporation of ageism over the decision to drop her from the BBC One show when it relaunched.