Taylor Swift and Justin Bieber are most polite celebrities

Taylor Swift and Justin Bieber have proved their politeness once again after they were named the world's Best Mannered celebrities for the second year running.

The two singers were both honoured for their etiquette by the National League of Junior Cotillions (NLJC) last year (11) and they are leading the pack once again in the organisation's 2012 nods.

NLJC national director Elizabeth Anne Winters says of Swift, "(She inspires) young people with her music and her manners... We think that she conducts herself with such graciousness with her fans. Keeping her dignity and poise as she created the Red album, and not really having anything that would sour her reputation."

Bieber was honoured for "consistently showing courtesy to his many fans," and British actor Daniel Radcliffe was feted for being nice to his Potter devotees, while Matt Damon was hailed as "a positive role model in Hollywood to younger generations".

British royal Catherine, Duchess of Cambridge was honoured for "the poise and dignity with which she conducts herself in the public spotlight", but her brother-in-law Prince Harry was named and shamed for his bad behaviour.

Harry was named The Most Ill-Mannered Person of 2012 for "disregarding his prestigious title and misbehaving in the public spotlight".

The dishonour is linked to Harry's infamous trip to Las Vegas earlier this year (12), when photos of the prince playing billiards naked surfaced online.