A senior teacher has won an out-of-court settlement from the NASUWT nearly four years after it failed to represent her when she was forced out of her job.
Patricia Webber was awarded almost Pounds 20,000 by an employment tribunal after quitting her job as deputy head at Lord Wilson School in Southampton.
She had suffered a series of problems, including a dispute over pay and lack of support when she returned after a period of sick leave.
But when Mrs Webber asked for her union's legal support in bringing her case, it refused.
Mrs Webber employed her own solicitor and was left with a legal bill of more than Pounds 30,000.
Since the tribunal ended in 2005, Mrs Webber has been fighting to have her costs reimbursed and had threatened to sue the NASUWT for breach of contract.
An out-of-court settlement for an undisclosed amount was reached last week, but Mrs Webber remains angry that the union did not represent her.
"There are thousands of teachers paying union subscriptions," she said.
"I always thought that if I got in trouble, they would be there to support me, especially with something like an employment tribunal. My union refused to help. They have battled for more than three years not to give me anything.
"This is not about the money, though. It is a matter of principle, and I want other people to be aware of it," she added.
Mrs Webber, who now works with pupils with behavioural problems, had been a teacher for 22 years when she resigned from Lord Wilson School in July 2004. She had been a joint deputy headteacher and head of PE, but had been forced to take sick leave after injuring her back. When she returned to work, Mrs Webber did not receive proper support, was undermined in front of staff and was excluded from a staff social event, the employment tribunal found.
Proper disciplinary procedures were not followed and complaints made by Mrs Webber were not properly investigated, it added.
The tribunal, which found that Mrs Webber had been the victim of unfair constructive dismissal, also raised concerns about the quality of advice given to her by her union.
Her NASUWT representative had sent an email criticising Mrs Webber, saying she "does not know her mouth rules her life".
The union representative expressed concerns that the head had coached staff on how to write letters of complaint against Mrs Webber, but did not use this information to help her case, the tribunal said.
The NASUWT denies that it mishandled Mrs Webber's case. Chris Keates, its general secretary, said: "The service provided by the union was of a good professional standard and the union's solicitors and counsel stated that we had a strong defence to the allegations if the case had proceeded to trial."