Ospreys fullback Lee Byrne left the field as a blood replacement © Getty Images

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Reaction: Tigers furious over 16th man

Matches: Ospreys 17 - 12 Leicester Tigers

Players/Officials: Lee Byrne | Sonny Parker

Tournaments/Tours: Heineken Cup

Teams: England | Leicester Tigers | Ospreys | Wales

Leicester Tigers have continued their efforts to ensure action is taken after the Ospreys briefly fielded a 16th man during their Heineken Cup defeat on Saturday.

The loss meant that Leicester slipped out of Europe at the expense of their hosts and Top 14 side Clermont Auvergne.

Ospreys fullback Lee Byrne returned to the field early from the blood-bin in the second-half and gave his side an extra man as Sonny Parker had not left the pitch, with Byrne re-joining the defensive line that thwarted a counter-attack from Tigers scrum-half Ben Youngs.

Leicester immediately confirmed that they had complained to ERC about the irregularity and have now sent an official letter of complaint to the tournament organisers as well as hire a leading firm of sports law specialists to represent them. Tigers chairman Peter Tom has also written a letter to his ERC counterpart Jean-Pierre Lux detailing their concerns.

"The Leicester Tigers board of directors have reviewed the footage of Saturday's Heineken Cup Pool 3 game against Ospreys and believe there is a clear case for concern," read a club statement. "The board has a duty to the club and the other teams in the competition to do everything in their power to help ERC to determine, as fully and speedily as possible, who was responsible for a 16th player being on the pitch.

"To that end, the club have lodged an official written complaint with ERC which they are now in the process of investigating. Everyone at the club is totally committed to supporting the investigation in any way they can."

Meanwhile, Biarritz have confirmed that their quarter-final against the Ospreys will be moved from their home ground, the Parc des Sports Aguilera, to the 32,000 capacity Estadio Anoeta in San Sebastian.