There could be something rotten in the heart of John Lydon. Last week came reports of a backstage fracas at the Summercase festival in Barcelona, when Kele Okereke, the Nigerian singer in Bloc Party, was allegedly subjected to a racist attack by the Sex Pistols singer and was left nursing a bruised face and a split lip when members of Lydon's entourage weighed in. And then yesterday he was reported to have sung boozily about "bloody Arabs" and "towel heads" during a lengthy pub session.

In the Barcelona episode, Okereke had approached him to ask about the possible reunion of Public Image Ltd, Lydon's post-Sex Pistols band. In Okereke's words, the singer became "intimidating and aggressive while his entourage responded with a racist tirade, including the statement, 'your problem is your black attitude'".

The incident was witnessed by several people, one of whom claimed that some members of Lydon's entourage behaved like "a gang of racist thugs". Three members of Lydon's crew are alleged to have punched Kele in the face and head as well as attacked Kaiser Chiefs' Ricky Wilson and Foals' Yannis Philippakis when they came to Kele's assistance.

Rather than delivering an apology for the behaviour of his crew, Lydon denied the allegations. Of the Okereke incident, he said: "We are in the middle of a wonderful tour. After 30 years we are achieving a true unity in our audience. They are multi-varied, all ages, all races, creeds and colours. When you are at a festival with bands who are jealous fools, lies and confusion usually follow." And he has been quoted denying having sung "any song that was racist towards Arabs or any part of mankind".

Lydon is a man of peculiar intelligence, brutal honesty and supposedly ironclad morality, so these charges are serious. A man born into a poor Irish background whose memoir of the Sex Pistols was entitled with righteous anger, 'No Blacks, No Irish, No Dogs'.

"It's not an issue of the physical assault, even though it was an unprovoked attack," Okereke remarked later. "It is the fact that race was brought into the matter so readily. I am disappointed that someone I held with such high regard turns out to be such a bigot."

Before we assume that Lydon has held these attitudes since the days of the Sex Pistols, it is as well to recall that the band's anti-Establishment stance was all-embracing and that many of the original punk audience comprised a large percentage of non-whites, who responded to the blazing energy and anti-authoritarian lyrics with alacrity.

The problem was that many other lesser groups (such as some members of Skrewdriver) who came up in the wake of the Pistols and The Clash were little more than skinhead thugs who subverted the original intent into something more sinister. The use of iconography such as swastikas and Union Jacks became less a deliberately ironic provocation and more a statement of intent.

"You must assault all mannerisms, all assumptions, all the things that cause us problems and cause us grief," said Lydon in a recent interview.

"The unspeakable should not be unspeakable. When you bring these things out into the open, you can tear them apart. It's no good pretending Nazis don't exist. They bloody well do, and they must be stopped."

The suggestion that he has abandoned his principles to become the worst kind of Little Englander is a worrying allegation to be made about a man who always seemed to be above the common herd and whose own bullshit detector was permanently set to maximum.

"The thing that keeps me ticking is my values," claimed the singer recently. "And I maintain them because they're worthy. I like to wake up and feel I've done no wrong."

Unless he is entirely bereft of conscience, Lydon's happy mornings may be over for some time.