Ukip leader Nigel Farage has been accused of ageism by Neil Hamilton as the public spat between them intensified.
Mr Farage - who is upset that the ex-Tory MP has been elected the party's leader in the Welsh Assembly - suggested his colleague was too old for the job.
But Mr Hamilton insisted that at 67 he was younger than Winston Churchill, Ronald Reagan and Clement Attlee in their political prime and said the jibe would annoy Ukip's elderly backers.
"The average Ukip member will be very disappointed at Nigel's ageist remark. Ukip has many thousands of active and vigorous senior members," he said.
"It seems particularly odd to knock old age at the very moment we celebrate the 90th birthdays of two icons of Britishness - Her Majesty the Queen and Sir David Attenborough.
"If Attenborough can still survive in a jungle of wild animals and predators at 90, I'm sure I'll be fine in the Assembly.
"Clement Attlee was 65 when, as Prime Minister, he introduced the NHS. Churchill was 72 when he led us to victory against the Nazis. Ronald Reagan was 77 when he brought about the collapse of the Soviet Union and ended the Cold War.
"Is Nigel suggesting he could have done a better job than any of them, because he is 15 years younger than me?"
Mr Hamilton re-ignited his political career when he first won a seat on the Welsh Assembly then successfully challenged Welsh party leader Nathan Gill for the leadership of its seven-strong group of AMs.
Mr Farage, who makes no secret of his dislike for his party colleague, had told LBC Radio: "I personally was not particularly in favour of Mr Hamilton's return to the frontline, aged nearly 70. But there you are, he's there, people have voted for him.
"I think it is difficult to return to frontline politics after a 20-year gap when you are getting on a bit in years.
"But there you are, perhaps he'll surprise me."