Feeling better ... Catherine Duchess of Cambridge.

Feeling better ... Catherine Duchess of Cambridge. Photo: Getty Images

The Duchess of Cambridge is attending the BBC's Sports Personality awards show in her first public engagement since leaving hospital for severe pregnancy sickness, St James's Palace says.

She will present the main award and lifetime achievement honour when Britain's top sports stars gather to celebrate a year of sporting achievement hailed as the nation's greatest ever on Sunday night (Monday morning AEDT).

The duchess has not been seen in public since leaving King Edward VII's Hospital in London on December 6.

The Duchess of Cambridge chats with David Beckham during the BBC Sports Personality of the Year Awards 2012 in London.

The Duchess of Cambridge chats with David Beckham during the BBC Sports Personality of the Year Awards 2012 in London. Photo: AP

She had received three days of treatment for a condition known as hyperemesis gravidarum, which leaves expectant mothers so ill they cannot keep food or liquids down.

Kate will attend the awards in her role as an official ambassador of Britain's Olympic and Paralympic team, St James's Palace said.

A spokesman said: "The Duchess of Cambridge will tonight attend the BBC's Sports Personality of the Year awards at the ExCeL London, where Her Royal Highness will present the lifetime achievement and the main sports personality of the year awards.

"The Duchess will attend the event in response to a long-standing invitation from the BBC."

Kate, who is less than 13 weeks pregnant, was ordered by doctors to have a period of rest at her home at Kensington Palace after leaving hospital.

She was recently forced to miss two royal engagements - a Centrepoint Royal Albert Hall fundraiser and the British Military Tournament.

- PA