The England full-back Mike Brown is unlikely to play again this season because he is continuing to suffer concussion symptoms two months after he was knocked out while playing in the Six Nations.

The 29-year-old was involved in a sickening collision with Italy’s Andrea Masi on 14 February but recovered to play in England’s final two games, against Scotland and France. He has suffered further symptoms since his return to Harlequins, with Conor O’Shea, the director of rugby, revealing Brown is still suffering from headaches “throughout the day”.

As a result Brown is not taking part in any training and has been ruled out of the games against Sale and Bath, with O’Shea saying the player will probably not feature against Newcastle on the final day of the regular season on 16 May. With Quins unlikely to reach the Premiership play-offs that would bring Brown’s season to a premature end but O’Shea is adamant the full-back’s World Cup participation is not at risk.

“Mike has played just six league games for us this season and it looks like it will probably stay that way,” said O’Shea, who suspects Brown picked up another knock against France. “He comes into see the medics but until he’s symptom free, he won’t resume any sort of training. It’s probably the wrong turn of phrase but it’s doing his head in because he can’t train and is very frustrated. He has headaches throughout the day.

“If it’s an ankle injury, you can grade it and set a timescale. This is more “how long is a piece of string?” Are we worried? Of course we’re worried. He didn’t even enjoy his week away. I feel for him.

“If I said to you ‘go home, you’ll have headaches for the next month and you don’t know when they are going to stop’ – well, that’s a pretty tough place to be and that is where he is at the moment.”

The news comes three weeks after George North was stood down by Northampton after being knocked out for the third time in two months but O’Shea has defended the England medical staff and insisted Brown will be fit in time for the World Cup.

He added: “How anyone can question the ethics of anyone on the medical side of this is beyond me. He has been treated excellently. He’ll have the World Cup warm ups and he’ll be fine. The World Cup is not an issue at all.”