In Indian general election of 2004 her party aligned with the Bharatiya Janata Party, however the alliance lost the election and she was the only Trinamool Congress member to be elected from a parliamentary seat from West Bengal. Banerjee suffered further setbacks in 2005 when her party lost control of the Kolkata Municipal Corporation and the sitting mayor Subrata Mukherjee defected from her party. In 2006, the Trinamool Congress was defeated in West Bengal's Assembly Elections, losing more than half of its sitting members.