I have known Amir Khan since his early amateur days, and probably have been closer to him than any other boxing writer. I was the only journalist who, with my family, was invited to his private World Championship-winning celebration party in Bolton last year. My two young grandchildren idolise him.

This is not written as a vainglorious piece of name-dropping but to emphasise how shocked I was to read in the "Screws" - our trade name for the News of the World – that he apparently was guilty of the sort of salacious behaviour more usually associated with delinquent footballers or sprauncy game show hosts.

It appeared that our Olympic silver medallist had been taking a leaf out of the text book - or rather texting book - of Tiger Woods and sending explicitly sexy messages to a buxom blonde. 

A|as, they were rather more than that. The messages were described as "lewd and obscene" and were accompanied pictures of his manhood. The lady in question was a topless model he had met in a Hollywood nightclub.

Topless models? Nightclubs? Obscene messaging?

I could not believe this was the Amir I know. But there you go. In modern sport such  raunchiness is par for the course - and not only Tiger’s. It seems that Bolton’s boy-next-door already has been seduced by the glitz of Tinsel Town, where he now resides under the tuition of top trainer Freddie Roach and promotional banner of Oscar de la Hoya’s Golden Boy.

I was disappointed when Khan left Frank Warren, who had initially nurtured, then revived, his career and took him to the WBA lightweight title. But he was entitled to do what he and his advisers thought best. I just hope he has done the right thing, and is not heading down the same hazardous path as one of his ring idols, Naseem Hamed. Another of his icons is Muhammad Ali. Well, he certainly seems to be in the Ali mould as a skirt-chaser.

No-one is suggesting that at 23 and unmarried, Amir should be leading a monastic existence, despite his firm religious beliefs - he and his family could be described as liberal Muslims. But since Amir went to Hollywood he seems to have become brasher and flashier.

It was only last weekend, after a ten days wait in Vancouver, where he had to move his training camp from Los Angeles, that Khan was granted a working visa for his second title defence against Paulie Malignaggi in New York on Saturday. Allied to the fall-out from the "Screws" revelations it is hardly then sort of preparation he would have wanted, and there has to be concern in the Khan camp, and among his sponsors, that Amir’s hitherto clean-cut image has been tarnished, at least temporarily.

Appearing at Madison Square Garden - albeit in the smaller 5,000 seater arena - should be a proud moment for Khan, who claims to be unaffected  by distractions which we must hope do not blight his career or the affection of the British public.

However I cannot quite agree with Barry McGuigan who, in his Daily Mirror column, says Amir was "not doing anything most red-blooded youngsters have not done." Surely it goes somewhat beyond that because Khan is not just any red-blooded youngster and has always said himself that he knows he is a role model for thousands of kids in Britain, not least the Asian community.

Of course is entitled to a private life - and a previously well-hidden sex life about which he talks illuminatingly to the ubiquitous Piers Morgan in the latest issue of GQ magazine. There he says that girl are "lining up" up to meet him in LA, adding: "They always come back so I must be doing something right."

In the same revealing article it seems rather ironic that, when asked what he thought about highly-paid footballers who misbehave he condemns than as being "weak." Ashley Cole and John Terry, he says "have shamed their families."

Of course it is not only footballers and fighters who need to be role models. Any sports personalities these days, especially Olympians, must maintain standards both in public and in private, that are beyond reproach.

Others who admit to being shocked by Khan’s behaviour are his former Olympic coach and father figure Terry Edwards ("Amir’s the last person I thought would do this sort of thing") and his one-time amateur buddy and professional stablemate Kevin Mitchell. "I was saddened to hear this stuff," says the unbeaten Mitchell, who is also engaged in a major fight on Saturday against Aussie hard man Michael Katsidis for the interim WBO lightweight belt at Upton Park.

"If nothing else, what was he doing in a nightclub while preparing for a world title fight? Amir is a lovely fellow and we’ve been good mates but I think all the money and hype has gone to his head. He’s obviously let the Hollywood lifestyle get to him. He’s beginning to believe his own publicity, even talking about fighting Manny Pacquiao or Floyd Mayweather next year.

"He’s not in their league. He’s too vulnerable. You can’t put muscles on his chin. If he couldn’t go a round with Breidis Prescott (the Colombian whom Mitchell later brilliantly outpointed) he wouldn’t last two rounds with them. He’s just making himself look foolish and I feel gutted for him."

If he and Khan ever meet the "Dagenham Destroyer" has no doubt about the outcome. "l may be smaller but I hit harder. I’d knock him out because I know how to. Knocking people cold gives me a buzz. In any case I think he’ll get beaten before I can get to him.

"I’ve heard Amir is getting over a million dollars for fighting Malignaggi. Bloody hell, for a million dollars I’d fight ten Mike Tysons."

Boxing will be blowing bubbles this weekend for not only is there the Mitchell-Katsidis scrap at West Ham but Mitchell’s amateur almer mater, West Ham ABC, have three club members in contention for titles in the ABA Championships at York Hall this Friday.

Ironically, the club which produced fistic notables like Billy Walker and Nigel Benn, has a fight if its own. Their training premises at the nearby Black Lion pub in Olympic heartland are under threat and soon they may be seeking new headquarters.

One of the shocks about this year’s ABA’s is the absence of the history-making European bantamweight champion Luke Campbell, from, Hull, who suffered a disputed defeat en route to the finals. Campbell has moved up to featherweight, a division that is particularly talent-rich. But the skilful Campbell still believes he can at least emulate Khan in 2012.

One to keep an eye on at York Hall is 20-year-old Finchley super-heavyweight Anthony Joshua, 6ft.5in and 17 stones, who, like both Khan and Mitchell, can box and bang, always a recipe for a winner. Meantime I hope my friend Amir will realise just how much he is risking with hisi regrettable indiscretions. From now he must mind his Ps and Qs. Not to mention his GQs.

Alan Hubbard is an award-winning sports columnist for The Independent on Sunday, and a former sports editor of The Observer. He has covered 11 summer Olympics and scores of world title fights from Atlanta to Zaire. Mitchell v Katsidis is live on Sky Sports HD1 from 8pm Saturday. Tickets available from Ticketmaster on 0844 847 2500. Khan v Malignaggi live on ITV1 from 2.45am Sunday.