Harlequins director of rugby Conor O'Shea has blasted the match officials following his side's 31-26 win at London Welsh in the Aviva Premiership on Sunday.

Quins returned to the top of the table thanks to the bonus-point victory, but O'Shea was far from happy with the performance of the referee and his colleagues.

"I'm unbelievably frustrated, you'd have to go a long way to see worse," he told Sky Sports News.

"Everything was wrong - it was incredible. The offside line was irrelevant, trailing runners coming back was irrelevant, backing into the maul, not releasing in the tackle - all irrelevant.

"We have a feedback process for the referees but it's not actioned upon and it's very difficult at times."

Harlequins resume their Heineken Cup duties on Saturday when they host Connacht.