McCririck was one of a number of faces dropped from the presenting team after Channel 4 awarded the production contract to IMG Sports Media, ending its previous agreement with Highflyer.
McCririck was vocal in his criticism of the decision when it was announced last October and has decided to pursue Channel 4 and IMG Sports Media through the courts.
In a statement issued to Press Association Sport, he said: "Channel 4 and production company IMG Sports Media were yesterday each served a letter before action for age discrimination.
"After 29 years with Channel 4 Racing, on a rolling annual contract, I have been sacked without any consultation or cogent explanation. I am 72.
"For loss of future earnings, unfair career damaging, public humiliation, stress and mental anguish, I will be seeking £500,000.
"Ageism is illegal. For tens of thousands of employees it has become the feared scourge of our society.
"This litigation should prove to be a watershed.
"There's no upper limit to the amount of damages employment tribunals can award under the Equality Act 2010.
"I am seeking a further exemplary, punitive £2.5m, part of which will be donated to charitable organisations helping to prevent negative prejudice in the workplace."
McCririck said he was being represented on a no-win no-fee basis by employment and sports law specialist solicitor Stephen Beverley, of the London West End Cavendish Legal Group.