Moss 'extremely serious' over Cowell song

Kate Moss has been busy training her vocal cords after agreeing to serenade Simon Cowell at his 50th birthday party, according to a report.

The supermodel has been tipped to perform a Marilyn Monroe-style 'Happy Birthday', jazz song 'Summertime' or a rendition of Lily Allen's hit 'Not Fair' at the event.

A source told The Mirror: "Kate agreed straight away. She is a keen singer and is taking her role in proceedings extremely seriously.

"As well as getting a few tips from her rocker boyfriend Jamie Hince, she's been practising her scales and gargling with lemon and honey."

X Factor winners Leona Lewis and Alexandra Burke have also been named as potential performers for the bash.

Cowell will celebrate his milestone birthday with hundreds of guests at Wrotham Park, Hertfordshire this weekend.