Alan Leighton, the national secretary of the referees union Prospect, said: "Mark Clattenburg deserves a full and unreserved apology from Chelsea. He deserves compensation for loss of earnings, damage to his reputation and stress.
"In addition, Chelsea should make a sizeable donation to Show Racism the Red Card and Kick It Out to help the fight against racism in football and beyond."
He added: "This was a charge brought on the flimsiest of evidence that should never have got to this stage. The internal inquiry mounted by Chelsea and their QC rested on a dossier of evidence consisting of just one witness statement in relation to the specific allegation against Mark.
"This matter should never have been made public and should have been dealt with confidentially."
More top news
The prime minister pitched her comments firmly towards unionists in her first campaign visit to Scotland ahead of the general election.
A police officer who spent six days crawling the London Marathon in a gorilla costume has finally completed the 26-mile route.
Nicola Sturgeon calls on voters to make sure "Scotland's voice is heard" and not "dragged back by the Tories" in upcoming vote.