McCririck spoke out last October at the time of the decision, which he blamed on ageism.
And he said in a statement released on Wednesday: "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."
I can not wait for the verdict on that one! Anyone know a recipe for humble pie served up with a good dollop of irony for quoting the equality act?