Prince William believes it is time to move on from the British "stiff upper lip" culture of burying one's emotions at the expense of their own well-being.

The Duke of Cambridge, whose brother Prince Harry has disclosed that he had therapy to help come to terms with their mother's death, said he and wife Kate Middleton want their children, Prince George and Princess Charlotte, to grow up in a world where they are able to express their feelings openly.

"There may be a time and a place for the 'stiff upper lip', but not at the expense of your health," the second in line to Britain's throne told CALMzine magazine yesterday as part of his support for mental health charity Heads Together.

"Catherine and I are clear we want both George and Charlotte to grow up feeling able to talk about their emotions and feelings," he told the magazine produced by the charity Campaign Against Living Miserably (CALM), which is dedicated to preventing male suicide in the UK.

As part of a wider campaign, the 34-year-old royal also highlighted the importance of people speaking out about their mental health in a video call with pop star Lady Gaga.

The pair chatted about how speaking freely on mental health problems can help shatter the stigma around them.

"It's time that everyone speaks up and really feels very normal about mental health, it's the same as physical health," William said.

"Everybody has mental health and we shouldn't be ashamed of it and just having a conversation with a friend or family member can really make such a difference."

Lady Gaga told the future king that her decision to reveal she suffered from post-traumatic stress disorder after she was raped at the age of 19 has changed her life.

"There is a lot of shame attached to mental illness, you feel like something is wrong with you... We have to make the strongest, most relentless attempt we can to normalise mental health issues," she said.

The release of a film of William's video chat with Lady Gaga on the Royal Family's Facebook page yesterday comes a day after his brother Harry took part in a podcast with 'The Daily Telegraph' in which he spoke candidly about how the death of his mother, Princess Diana, when he was 12 deeply affected him.

The two princes, along with the Duchess of Cambridge, are promoting the Heads Together mental health campaign as the annual London Marathon's charity of 2017.