The union at the centre of Birmingham's crippling bin strike had a “pervasive fraud environment”, a leaked auditors’ report has concluded.

Global tax advisory firm BDO found there had been a culture at Unite that “did not challenge the appropriateness of transactions” and failed to ensure appropriate financial reporting.

It concluded “dominant personalities and a weak control environment facilitated opportunities to commit fraud” at the union.

The audit was ordered by general secretary Sharon Graham shortly after she entered her role in 2021 amid questions about accounting and spending on building a hotel and conference centre in Birmingham.

Its findings were presented to the union’s executive council on Friday.