Independent media watchdog the Presswise Trust has accused The Sun of urban myth-making by printing a story that alleged asylum-seekers were stealing and eating swans.
The front-page exclusive, headlined "Swan Bake", appeared in the newspaper on 4 July and prompted a complaint from a group of refugees living in the UK.
The group was advised by Presswise and wrote to the Press Complaints Commission alleging a breach of clause one of the Editors' Code of Practice, which governs accuracy.
The story said: "Callous asylumseekers are barbecuing the queen's swans. East European poachers lure the protected Royal birds into baited traps, an official Metropolitan Police report says."
Presswise asked the police about the alleged incidents and found that no one had been charged with any such offence in relation to swans.
The Sun printed a clarification on page 41 of the paper on Saturday that was agreed with the PCC.
It stated: "While numerous members of the public alleged that the swans were being killed and eaten by people they believed to be Eastern European, nobody has been arrested in relation to these offences and we accept that it is not therefore possible to conclude yet whether or not the suspects were indeed asylum-seekers."
According to Presswise, The Sun has not gone far enough.
A spokesman said: "There is no solid evidence to support a sensational story that has entered the public imagination, yet five months later The Sun is simply obliged to run a disclaimer that it confused conjecture with fact."
By Dominic Ponsford