Kate Middleton Pregnant St James’s Palace Confirm
Celebrities have been congratulating the Duke and Duchess of Cambridge on Twitter. (Reuters)

Celebrities have tweeted congratulations to the Duchess of Cambridge on her pregnancy.

The news that Prince William and Kate Middleton were expecting their first child was confirmed by St James's Palace and sparked hundreds of messages of support from stars and well-wishers around the world.

Cheryl Cole wrote: "I'm sooooooo excited that we're having a royal baby !!!! Congratulations to Kate and Wills !!!!!!"

Even though Kate recenty refused to wear clothes from her new range, Khloe Kardashian said: "Congratulations to the Duke and Duchess of Cambridge!! A royal baby!!! :) awwww so sweet."

Piers Morgan ‏joked: "Hardly surprising Kate's feeling so sick - according to the National Enquirer, she's been pregnant since 2003"

Similarly, David Walliams responded to another user, who suggested that his baby, expected in the New Year, could marry the royal baby.

He wrote: "Your baby, their baby - you could be a future monarch's father in law!! That was always the plan."

Labour leader Ed Milliband said: "Fantastic news for Kate, William and the country. A royal baby is something the whole nation will celebrate."

Tennis ace Boris Becker said: "Two thumbs up to Will and Kate on their baby news. I wish them both the very best. Boris"

Richard Branson said: "Congrats to Kate & Will on expecting your first child. The happiest day of your life to look forward to!"

Former X-Factor star Diana Vickers said: "Oh, a Kate and Will baby!!!! wahooooo! ", while US star Demi Lovato wrote: "Kate Middleton is gonna have a baby. Been a great year for the brits!"