Duffy and Coldplay have led the way in the nominations for the 2009 Brit Awards with four each.
The Welsh singer will go up against Chris Martin's band in the best British album and single categories.
Singer Adele, Mercury Prize winners Elbow and Scouting For Girls have three nods each while Ting Tings, Radiohead, Girls Aloud and Estelle have two each.
The awards, co-presented by Kylie Minogue, James Corden and Mathew Horne, will take place on 18 February.
The nominations were announced at a launch party at the Roundhouse in Camden, north London.
Coldplay - who are leading a strong UK showing at next month's Grammys with seven nominations - are also up for best British live act as well as best British group, taking on Elbow, Girls Aloud, Radiohead and Take That.
Duffy, whose debut album Rockferry was the biggest-selling album in the UK last year with 1.685 million sold, is up for best British female and is a strong contender for best breakthrough act.
Florence is critics' choice
Coldplay go head to head with Rockferry with their album Viva La Vida or Death And All His Friends in the British album category, with their single Viva La Vida also taking on Duffy's Mercy.
They will be up against Elbow's The Seldom Seen Kid, Radiohead's In Rainbows and The Ting Tings' We Started Nothing for best British album.
Adele, the winner of last year's Brits Critics' Choice award, will compete against Duffy for best British female and best breakthrough act and is also up for best British single for Chasing Pavements.
Scouting For Girls, meanwhile, are up for best British live act, breakthrough act and single, for Heartbeat.
Backstage, singer Roy Stride said: "To get a live nomination as well is really special because we have played so many shows this year. We have the most amazing fan base in the world.
"It's the kind of things that bands say but we really mean it, but without then we're back working part time."
In the international category, the same five bands - AC/DC, Fleet Foxes, The Killers, Kings of Leon and MGMT - are up for the best group and best album awards.
Nominees Kings of Leon will play at this year's ceremony
Veteran Neil Diamond and bluesman Seasick Steve, both 67, go head to head with Kanye West, Glastonbury headliner Jay-Z and Beck.
Seasick Steve, whose real name is Steve Wold, admitted his knowledge of the Brits was very limited: " I didn't know what the Brits was 'till a couple of days ago and they tell me it's an honour.
"I can't believe any of it, it's like some kind of strange dream and that England has done this for me and been so nice to me, I'm real grateful."
It was announced after the launch party that Coldplay and Take That, who last year won the trophies for best British live act and British single, will be playing at this year's ceremony at London's Earls Court.
Other performers on the night include U2, Kings of Leon, Duffy, Girls Aloud and the Pet Shop Boys, who will receive an outstanding contribution to music award.
Florence and the Machine, the winner of this year's Critics' Choice award, will also perform.
The singer, real name Florence Welch, also came third on the BBC's Sound of 2009 new music list.
Fans will be able to vote for their favourite British single, live act and breakthrough act from the shortlists.
The best British single will be decided on the night of the main ceremony by a live telephone vote.
The Brits Academy, made up of 1,000 invited music industry insiders and critics, will decide on the remaining eight awards.
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