The 68-year-old will play the character in three new episodes to air next month before filming a final two-parter next year.
"It's time to move on. Frost is getting a little long in the tooth - it's time for Frost to hang up his coat and scarf," Sir David commented at a London press conference.
The actor added that there will not be a dry eye in the house when the inspector solves his last case.
"Perhaps he just retires gracefully, gets the gold watch and walks away from Denton nick, tears all round. He just hangs up his hat," he said.
Last year, Jason signed an exclusive deal with ITV preventing him from working for any other broadcaster.