Activists from a fathers’ rights group have scaled the roof at Buckingham Palace and displayed a banner reading, “I am Harry’s dad”.

Police were called at around 4.30pm local time (3.30am AEDT) after the pair climbed onto the roof of the Queen’s Gallery at the royal residence.

It is believed two men were able to use a ladder to breach the walls of the royal palace in London after a third person was able to create a distraction.

The building houses royal art and is open for public viewing.

The Fathers Justice Facebook page has named the pair as Martin Mathews and Bobby Smith.

The stunt has been claimed by the New Fathers 4 Justice and Stop The War On Dads groups.

The activists campaign for equal rights for fathers in divorce and separation proceedings.

Mr Smith stood against British prime minister David Cameron in this year’s general election and wore an Elmo suit during official campaign appearances.