The Hollywood actress, 35, is the latest to join the new series, which starts next week.
She will be joined by Whitney Houston's ex-hubby Bobby Brown, who has previously battled drug addiction.
Bosses hope party girl Tara will whip up some rivalry with fellow blonde Pammy.
But insiders claim the former Baywatch star won't be hanging around for long due to a contract that states she can leave after five days.
An insider said: "Both women are very feisty and producers hope that sparks will fly."
Others set to appear include "Big Fat Gypsy Weddings" star Paddy Doherty, Kerry Katona and her mum Sue.
Irish twins Jedward have signed a deal to take part while the House of Commons Speaker's wife Sally Bercow is also set to join the house.
Tara got engaged to Internet entrepreneur boyfriend Michael Axtmann last year but they split months later. She has previously starred in movies such as "The Big Lebowski" and shows including "Saved By The Bell: The New Class" and "Scrubs."
Pammy, 44, has previously appeared in "Australian Big Brother" - where she stayed for three days - and on "Dancing With The Stars" in the U.S.
Brown, 42, divorced Houston in 2007. He has appeared on a range of reality shows in the U.S. including "Celebrity Fit Club."
He has struggled with drug addiction and was jailed for drink driving in 2004.
"Ultimate Big Brother" winner Brian Dowling will take over from Davina McCall as host of the new look show, which launches on August 18.