An anti-monarchy group has launched a major new billboard advertising campaign against the British royal family.

"As we approach the end of the Queen's reign the country needs an honest, grown-up debate about the monarchy. We need to stop and ask ourselves: Can't we just choose our next head of state?," said the group known as  Republic.

According to the British media, the group has launched a billboard campaign across the UK with slogans questioning the British monarchy. The reports said Prince Andrew, who is facing sexual assault allegations, is the group's first target.

"We want the country to know there is a positive, exciting, democratic alternative to sitting back and letting Charles become our head of state. And we want the country talking about why the monarchy is bad for Britain, why it's time to call time on the royals," said the group.