A former Liberal Democrat councillor has made his first appearance on the Labour benches.
Coun Rupert Oliver has represented the Bowling ward, later Bowling and Barkerend, since 2003.
He quit the Liberal Democrats in July following a series of disagreements - in particular over its support for the Conservative leadership.
Coun Oliver said: "Leaving the Liberal Democrats was a tough decision, but under the current leadership in Brad-ford they have no vision, strategy or direction.
"I raised repeated concerns about the direction the group was taking but was ignored.
"The final straw was being told to vote for Conservative leadership of the Council."
In May, following the local elections, a deal was struck between the Conservatives and Liberal Democrats to allow the Tories to continue running Bradford Council.
Coun Oliver said: "I have come to the view that the best chance of improving the quality of life for residents of Bowling and Barkerend is through the Labour Party." Councillor Ian Greenwood, leader of the Labour Group, welcomed the move.
He said: "Rupert is committed to tackling key Labour priorities for the district, such as education, crime and drugs and securing economic regeneration. I am pleased he has decided his values and priorities are better represented by the Labour Party than the Liberal Democrat group."
Liberal Democrat group leader Councillor Jeanette Sunderland said: "He has been very inconsistent in his approach to being a councillor in the last few years.
"I am surprised to see his support for the Labour group, given that he argued with us not to support them after the elections.
"He should resign his seat and stand as a Labour candidate."
In May 2005 Coun Oliver made a bid to challenge Coun Sunderland in a leadership battle but was defeated 12 to two in a vote.
In 2001, he was suspended from the group for a month following an outburst. He was reported to the Standards Board for England, which decided not to investigate the matter.