The former England hooker Brian Moore has branded Manu Tuilagi a "complete and utter prat" for his prank when the British & Irish Lions gathered at Downing Street on Monday afternoon.

Tuilagi gave David Cameron "bunny ears" while stood behind the prime minister as a group of players and management posed for a photo at the function to honour the Lions' 2-1 series victory over Australia.

The 22-year-old Leicester centre subsequently apologised on Twitter, but while Moore believes it was a foolish act, he insists he should be spared punishment by England's management. "My real objection is it wasn't very inventive," Moore told Talksport. "People are saying they are offended. Are they really offended, or is it more a case of Tuilagi being an absolute prat again and taking the attention away from his team-mates?

"He has been a complete and utter prat. He ought to grow up, it's as simple as that, but people saying they are offended, are they really offended? The authorities, I'm sure, will do what they should do and say: 'Manu, everyone thinks you are a two-year-old, do you really want that? Now go away and grow up please.'"

He was echoed by Matt Dawson, an England World Cup winning scrum-half, who tweeted: "Pls explain why doing bunny ears is funny on any photo. All it show is the bunny is more famous than u and u want the limelight. #insecure".

Using Twitter to express his remorse, Tuilagi had said: "Apologies for messing around on Lions photo. No offence intended. Great Day at Downing Street. Thanks to Prime Minister for hosting us."

Leicester Tigers said on Tuesday that Tuilagi would send a written apology to David Cameron for making the gesture outside Downing Street.

Their director of rugby Richard Cockerill said: "It was just stupid. He's a young lad but he should know better. I've reminded him of his responsibility this morning.

"He's apologised on Twitter and will be writing personally to the Prime Minister to apologise for his behaviour and rightly so.

"Manu is in a privileged position and it is a privilege to go down to Downing Street for such a visit. He's a bit of a 'Jack the lad' but clearly you can't do that kind of thing.

"It's disappointing more than anything else. He knew he shouldn't have done it the moment he did it. He's in the glare of the media the whole time and, certainly, the Prime Minister is."

David Cameron has played down the incident, tweeting: "@Manutuilagi it was great to welcome you and the @lionsofficial team to No10. No need to apologise, I know it was just a bit of fun."

It is not the first time Tuilagi has been the centre of controversy – he was fined £3,000 by the Rugby Football Union for jumping from a ferry after England's calamitous World Cup campaign in New Zealand two years ago. He was cautioned by police on that occasion and disciplined by then England coach Martin Johnson.

Following his latest prank, Tuilagi's team-mates reacted on Twitter. Ben Youngs, a fellow British & Irish Lion, England and Tigers player, tweeted: "The man@Manutuilagi just couldn't stop himself."

The scrum-half later removed the tweet and posted a picture of himself posing outside 10 Downing Street.

Gloucester's fly-half Freddie Burns tweeted: "Great bottle from Manu Tuilagi! Haha. £chief."