Boris Johnson's father described his "pride" in being called a "non-cooperative crust" by his own son when approaching climate change activists.
A new wave of disturbing action from the Extinction Rebellion movement has shut down central London this week.
The prime minister addressed the protesters' action while attending the release of the third volume of Margaret Thatcher's authorized biography on Monday night.
Who is the extinction rebellion?
He told the guests, "I'm afraid the security people don't want me to go tonight because they said the road was full of crust and uncooperative protesters … scattered across the road."
But speaking to a crowd of supporters of Extinction Rebellion in Trafalgar Square on Wednesday, his father Stanley Johnson made little of his son's comments.
"With regard to uncooperative crusts, I wear this badge with pride," he said.
"It's one of the coolest things he's been saying about me for a long time.
"An uncooperative crust absolutely superb – do they taste good? That's my thinking, I think so."
Stanley Johnson, who has long worked on environmental issues, also told the crowd that the prime minister "absolutely supported the objectives" of his campaign.
Speaking later to the Press Association, Stanley Johnson emphasized that his family does not differ in their views on climate change.
"With regard to climate change, family dynamics would be totally united," he said.
"I don't believe there is a single dissenting voice in the Johnson family.
"Do not forget that we grew up in the country, we grew up in Exmoor, nature is in our blood.
"I don't think you need to say & will he (Boris) listen? & # 39;
"If you hear what he said on the steps of Downing Street that first day, he ended up with a call for movement on the environment and animal welfare.
"And that's a very, very good sign."
Prime Minister's father says his family is "united" on climate change
Stanley Johnson added that he considered the Rebellion Extinction action "tremendously important."
"From small acorns, big movements come up," he said.
"This is a movement, it is a very important movement. It is absolutely clear to me that we have been moving very slowly on the issue of climate change."
Nearly 600 protesters were arrested during the early days of the two-week Extinction Rebellion demonstration in the capital, police said.
Activists closed roads and clung to buildings.
Anyone who fails to comply with a police order to meet only in Trafalgar Square's pedestrian area is subject to arrest and prosecution.