Public Image Ltd, Academy, BirminghamJulian Casablancas, Forum, London

Even though John Lydon is flogging butter on the telly, his Public Image is above criticism

Old Man Steptoe leers over his lectern, and lectures. "Seventeen seconds, or 17 years. It will be worth the money. This is the band who taught all the other second-rate wankers out there how to play. I do apologise..."

He speaks the truth. In Public Image Ltd, John Lydon is in his element. During the last round of Pistols reunions, in his Rotten persona, he pointedly wore a PiL shirt on stage.

In 1977, while still a Sex Pistol first time round, Rotten amazed fans by appearing on Tommy Vance's Capital Radio show and choosing nothing but obscure reggae records. It was a hint of what was to come. Public Image Ltd broke punk's DNA wide open, unravelled the rainbow and reconnected it into new shapes, using deep dub and funk noir. Post-punk starts with PiL.

It would take a fusspot or a fool to complain about a band who, from the first "Hello, hello, hello!" to the climactic "Anger is an energy!" (in a set that's more than two hours long), are note-perfect. Highlights are "Poptones" ("Shame on you," he mocks. "It's a song about getting raped, and you're applauding"), the provocateur-funk of "This Is Not a Love Song", a rockin' "Annalisa", a surprise encore of Leftfield & Lydon's "Open Up" and a double-length "Flowers of Romance".

Even so, you're always waiting for a song to end, just to see what he'll say next. Lydon is the ultimate pop hero: a working-class autodidact with Celtic ginger hair, an intellectual (oh, how he'd spit at that term) who recognises the intellectual's duty to antagonise.

He never ducks that duty. Swigging Martell and gobbing it into an ice bucket like it's dentist's mouthwash, he puts one finger to his nostril and expels snot through the other. "Notice," he caws, "I spit away from other human beings. Something those silly punks who read The Sun got wrong."

While he's in the mood for setting the world to rights, lest anyone in the English Defence League misunderstand lyrics like "This is our country... we will never surrender", Lydon follows "Warrior" by stating, "Great Britain is a mixed country and we like it that way. The only people who have to leave are the politicians."

He cleverly sidesteps any "sell-out" heckles regarding his recent hawking of dairy products dressed as a British country sire. When his trousers start falling down past his skinny arse, he cackles, "Fackin' 'ell. All that butter, and I've still lost weight."

So, the race is on. On the one hand, there's "West End" Joe McElderry doing a Miley Cyrus song. On the other, there's the internet campaign to stop The X Factor winner by getting everyone to buy a petulantly sweary Rage Against the Machine single. Crushed in the middle there's the valiant but doomed Facebook group trying to stop both of them with Darlene Love's immaculate Spector classic "Christmas (Baby Please Come Home)".

What's gone almost unnoticed, among all the fuss, is that someone's released a decent Christmas song that's actually about Christmas this year. And that someone, most surprisingly of all, is slack-mouthed Strokes singer Julian Casablancas, whose cover of the Saturday Night Live crew's "I Wish It Was Christmas Today" is a Ramones-meets-Wizzard cracker. Of course, before we get to that inevitable festive finale, audiences at JC's solo shows have to stand through the bulk of his Phrazes for the Young, whose Wildean title becomes even more ironic when confronted with the wit-starved stage presence of Casablancas. "Wooh shit yeah!" he quips, slumped over the mic. "You guys are fuckin' awesome. Shit yeah!" Johnny Rotten he ain't.

In fairness, his solo material isn't bad, from the space-age Nashville of "Ludlow St" to the crazed, atonal funfair bleeps of "River of Breaklights" (sic), and his six-piece backing band are more haywire than the tightly drilled quartet who usually stand behind him. "Fuck yeah London, how you doin' tonight?" he asks during a lull, then displays the briefest flicker of self-awareness – "I have to say that" – before the amiable airhead reverts to type with "OK, let's do this shit".

He isn't called back for an encore, but does one anyway. Calls for "Last Nite" or "Juicebox" are fruitless. Instead, we're palmed off with a Strokes B-side, "I'll Try Anything Once". Embarrassingly, Casablancas doesn't know the words. Fortunately, neither does anyone else.