A carnival atmosphere prevailed at Lily Allen’s packed Manchester show on Saturday, and not just because of the jaunty ska rhythms and summery calypso melodies in her music. Allen, who is playing a string of British dates to warm up for her first major US tour, remains Britain’s favourite naughty little sister, smoking and swearing and sweetly skewering her chart rivals between songs.

Skipping onstage in a red-and-white party frock, the pint-sized pop princess needed no charm offensive. She had us at hello.

Allen’s inspired blend of old and new, emphatically English fairground pop and borrowed Jamaican rhythms, bittersweet lyrics and am-I-bovvered attitude can feel a little calculated on record. But it sounded totally natural live on Saturday, with a full band plus brass section adding depth and texture to the slick studio polish of her best-selling album Alright, Still.

After her suspiciously smooth overnight success last summer, some predicted Allen would be a short-lived pop novelty. But nine months on, infectious singalongs such as LDN and Everything’s just Wonderful have lost none of their lustre.

Indeed, Allen’s absurd lack of recognition at last month’s Brit Awards has only reinforced her image as a populist underdog, despite her famous parentage and privileged background. Like Kathy Burke or prime-time Robbie Williams, Britain has adopted the 21-year-old singer as a kind of classless national mascot, with America on the brink of following suit.

The teeming Manchester audience was certainly testament to Allen’s pluralist, pan-generational appeal. While fortysomething mums and dads jigged along to her nostalgic ska rhythms, toddlers beamed approvingly at her sunny nursery-rhyme melodies. Meanwhile, teenage girls lapped up the singer’s cheerfully merciless lyrical postmortems on former boyfriends and their sexual shortcomings. For all her cruel insights into male failings, young men clearly find Allen alluring too, although one group near me became vocally appalled when she spat on stage. How unladylike.

Although her compact set came in around the 80-minute mark, Allen made up for any shortfall with charm and humour, apologising for the brevity of her album and lack of extra material. However, she did play a clutch of unreleased tracks including Absolutely Nothing, an unusually downbeat ballad unleavened by her usual breezy wit. She also bulked out the set with cover versions. The best of them, Blondie’s Heart of Glass and Blank Expression by the ska-pop icons the Specials, both date from before Allen was even born.

Two of her finest observational vignettes, Friday Night and Knock ’em Out, provided back-to-back highlights late in the set. These mellifluous mini-dramas about the tensions of clubbing and drinking in Blair’s Britain are not just fully rounded songs but potential goldmines for future social historians.

Inevitably, Allen’s breakthrough chart-topper Smile was saved for the climax. But she ended the set with her latest single, Alfie, a sweetly protective tribute to her younger brother. With its belting vocal and oompah rhythm, the song sounded uncannily like Sandie Shaw’s 1967 Eurovision winner Puppet on a String. Perhaps, after conquering America, Eurovision should be the next target for Britpop’s reigning carnival queen. On her current indestructible form, it would be a walkover. Lily Allen plays London Hammersmith Apollo tonight

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