UNITE general secretary Sharon Graham remains “determined to get to the truth” after the Serious Fraud Office launched a probe into the construction of a hotel and conference centre owned by the union.

Some £112 million was spent on the project in Birmingham, which was completed in 2020, but the building was later valued at just £29m and a KC-led inquiry commissioned by Ms Graham identified a “mystery” £14m which does not feature in the final accounts.

A Unite spokesman said Ms Graham, who took over as general secretary in 2021, “has had to endure repeated attacks by those with much to lose since she launched these inquiries, from both inside and outside the union.”

Unite added it that it had put safeguards in place to ensure “such things can never happen again.”