The prospect of becoming a grandfather to the baby of Prince William and his wife Catherine has strengthened Prince Charles's determination to fight climate change, he said in an interview broadcast Monday.

The heir to the British throne, an outspoken environmental campaigner, said he did not want his first grandchild to ask him why he had not done more to halt climate change.

Prince William and Catherine, both 30, announced her first pregnancy in December and their baby is expected this summer.

"I don't want to be confronted by my future grandchild saying, 'Why didn't you do something?'" Charles, 64, told ITV.

"So clearly, now that we will have a grandchild, it makes it even more obvious to try and make sure we leave them something that isn't a totally poisoned chalice."

Charles said he did not want to "hand on an increasingly dysfunctional world" to the baby, who will be third in line to the throne after him and William.

Catherine spent four days in hospital last month being treated for severe morning sickness.

If the baby is a girl, she will be the first in the British royal family to become queen even if she has a younger brother, after the Commonwealth announced historic changes to the laws of succession in 2011.

Charles has long been an advocate of stronger environmental protection and set up the Prince's Rainforest Project in 2007 to campaign against deforestation.

In a wide-ranging interview with ITV he also spoke of his fears for his younger son Prince Harry, who is serving with the British army in Afghanistan as an Apache helicopter pilot.

"If you are a parent or relation or loved one and that person is away in these incredibly dangerous and challenging circumstances, I know you worry all the time," he said.

"Certainly every night I worry. But he (Prince Harry) loves doing what he's doing and he's brilliant at it."