LONDON (Reuters) - British anti-monarchists said on Sunday that they planned to protest during the coronation of King Charles in May, saying the ceremony was "a slap in the face" for most people struggling with high inflation.

Campaign group Republic said it had been in contact with London's police force about its plans to hold a peaceful demonstration in Parliament Square, which is overlooked by Westminster Abbey where British monarchs are crowned.

"The coronation is a celebration of hereditary power and privilege, it has no place in a modern society," Graham Smith, Republic's chief executive, said.

"At a cost of tens of millions of pounds, this pointless piece of theatre is a slap in the face for millions of people struggling with the cost-of-living crisis."

Buckingham Palace said on Saturday that the coronation would be celebrated with processions, a concert at Windsor Castle, street parties, light shows and community volunteering.

Charles, 74, became king in September after his mother Queen Elizabeth died. The coronation will take place on May 6.

Polls have shown most Britons back the monarchy but Republic claimed that support was on a "slow puncture."

(Reporting by William Schomberg; Editing by Tomasz Janowski)