Referees missed out on officiating top rugby matches because selectors were unfairly critical of their body shape, the Rugby Football Union has admitted.

The issue was initially brought up by former referee George Richardson.

"My primary motivation for raising the complaint was to ensure there is cultural change," he said.

"[I want] to ensure that in the future assessments are based on ability to do the job, not physical attributes.

"I wanted to make sure that learning has taken place across the RFU refereeing pathway, so that the best referees within the country can get to the top and rugby really can be "the all-inclusive game".

The RFU said the report's findings were "unacceptable" and apologised for "the negative impact this has had on the referees concerned".

"The investigation found while there is no formal policy regarding referees' weight, size or shape it has nonetheless been part of the criteria for assessment, regardless of whether fitness assessments were passed," it added.

"The report also identified these criteria as being recognised at the highest levels of officiating and that this appears to have had a trickle-down effect.

"The RFU is committed to addressing these practices to ensure physical appearance will not form part of selection criteria in future."

The report's authors spoke to nine other referees who had experiences similar to Richardson.

The RFU has brought in a new code of conduct for those training and picking officials, and has emphasised how officials can report unfair feedback.