The Californian, who competed in his second full season at NASCAR's top level this year, having switched from Formula 1 where he raced for Scuderia Toro Rosso until the middle of 2007, is claiming breach of contract in a suit filed this week in a North Carolina Superior Court in the United States.
Although Red Bull had initially picked up an option it had on Speed's services this year, the team's general manager Jay Frye had said back in October that there were performance clauses that Speed needed to meet in order to keep his drive, with the 27-year-old claiming at the time that he had a signed contract for 2011.
In his first full season in the Sprint Cup Series in 2009, Speed finished 35th in the drivers' standings while this year, despite a solid start that saw him break inside the top 12 in the points, he slid down to 30th in the championship by the end of the season.
Speed and Brian Vickers were both candidates for the remaining seat in the team for 2011 alongside Kasey Kahne, who will drive one of the team's Toyota Camrys before he moves on to Hendrick Motorsports in 2012.
Kahne drove the team's # 83 car in the last five races of the year, taking a sixth-place finish in the season finale at Homestead, where he started from pole position. Speed finished 23rd in that same race, his best result over the last five races of 2010.
Vickers, who has been sidelined from racing since May after being diagnosed with blood clots, will be Kahne's team-mate next season following successful treatment. Vickers gave the team its maiden and only victory in the Sprint Cup thus far by winning from pole at Michigan last year.
Speed is expected to remain in NASCAR despite not having any firm plans for 2011.
Kahne to finish 2010 with Red BullPalop commits to Sevilla
