Cherie Booth QC is joining the Merseyside comedian Ken Dodd to promote Liverpool as a cultural destination.
The PM's wife said Liverpool is the best place for culture
The city council launched an 08 Ambassador Programme to help spread the word about the city being European Capital of Culture in 2008.
The city is expecting two million extra tourists that year, which it is hoped will generate £200m for the economy.
The Prime Minister's wife said "I support Liverpool because it is the best place for culture today."
Ken Dodd, 79, said: "I am proud to be a citizen of Mirthyside. It has a great heritage of comedy performances."
"So many of my heroes have lived and worked in this wonderful city of colourful characters.''
Cherie Booth QC
Paul Heathcote, chef
Brian Jacques, author
Archbishop Patrick Kelly
Gerry Marsden MBE, singer
George Melly, musician
Stephen Parry, swimmer
Jazz musician George Melly and singer Gerry Marsden will also support the campaign, along with Archbishop Patrick Kelly, swimmer Stephen Parry and chef Paul Heathcote.
Ambassadors will receive a welcome pack including a fact sheet about the city's cultural assets, a special ambassador badge and regular updates about Liverpool as the city builds up to the big year.
Councillor Warren Bradley, Leader of Liverpool City Council, said: ''We want everyone who loves Liverpool to tell the world about why Liverpool is a great city to visit and why it will be a brilliant European Capital of Culture in 2008.
''Ambassadors can come from all walks of life but having such famous Liverpudlians who perform all over the world will be a great boost.
"By providing up to date news we can ensure people can talk about the city knowledgably and with pride. This army of friends will give Liverpool the best type of recommendation - by word of mouth.''