A former Labour MP has been awarded £75,000 in damages and may seek more than £1m in legal costs after suing Unite for libel over an article that claimed she acted dishonestly while applying to become a member of the union.

Anna Turley took Unite and a journalist, Stephen Walker, to the high court over a story that appeared on Walker’s Skwawkbox blog in 2017.

During the court hearing in November, Unite’s barrister told the court that Turley was unfit to be an MP. Turley lost her seat of Redcar to the Conservatives last week.

On Thursday after the court’s ruling, Turley said she was “thrilled and relieved” to win. “I am very pleased with today’s verdict, and to be able to say that I have won my libel action against Unite the Union and Skwawkbox,” she said. “It gave me no pleasure to undertake this action, but the accusations were so serious and damaging to my reputation that I had no choice but to defend myself through the courts.”

Court costs are still being assessed but Turley’s legal team are expecting to seek more than £1m, taking into account success fees and insurance. Unite and Walker are jointly liable for costs and damages but the union has reportedly paid all the journalist’s legal fees.

Costs in the case were built up after six days in court, with nine witnesses called, as well as witness statements from another five people.

The case related to Turley’s application to join Unite, which is Labour’s biggest donor, in December 2016. She submitted it a day before the announcement of a Unite election for general secretary. The incumbent, Len McCluskey, one of Jeremy Corbyn’s most influential advisers, was facing a possible challenge from a moderate candidate, Gerard Coyne.

An article appeared on Skwawkbox in April 2017 claiming that Turley had broken the rules by joining Unite’s community section, which was supposed to be exclusively for unwaged members, and that she had made a false declaration to do so.

A Unite spokesperson was quoted in the article as saying: “Anyone joining on a fraudulent basis will prompt an investigation. A complaint has been received and is being investigated.”

According to Turley’s counsel, she joined as a Unite community member and was told by Unite in March 2017 that she should move to become an “industrial” member. Turley replied days later apologising and asking how she should transfer her membership.

Kate Wilson, for Turley, said the Skwawkbox article in April 2017 conveyed the meaning that Turley acted dishonestly in submitting her application.

A barrister representing Unite and Walker told a judge that Turley had been dishonest and “regrettably” was not fit to be an MP. Anthony Hudson QC told Mr Justice Nicklin that Turley’s dishonesty “permeates through every part of the case”. He claimed she had been “deceiving people so she could vote against Mr McCluskey and oust Jeremy Corbyn”.

Turley told the court that the Skwawkbox article made “false and defamatory” allegations about her and impugned her honesty. “I had not dishonestly joined the community section of Unite and there was no reason to suspect me of being dishonest. I believed I was entitled to join it,” she told the judge.

“I am not dishonest and have not lied or sought to mislead. My reputation for honesty and integrity are of the utmost importance to me. They go to the root of who I am and why I am in public service.”

According to court documents, Turley applied to join Unite Community after she read about the challenge to McCluskey’s leadership on a confidential WhatsApp group for Labour moderates, known as the the Birthday Club Group.

Spokespeople for the union said it was “very disappointed” with the decision. “The union does not agree with the court’s findings on several points of law … Unite will therefore be appealing the decision.”