Unite is facing a £70 million hole in its finances over a hotel investment overseen by Len McCluskey, it has emerged.

The Labour-affiliated trade union spent almost £100 million on a hotel and conference centre in Birmingham after costs spiralled over the course of its construction.

It is understood that Sharon Graham, who became the Unite general secretary in August, told a video call of officials last week that two valuations of the complex came in at between £27 million and £29 million.

A Unite source told HuffPost UK: “Sharon Graham feels like she has been handed an unholy mess and now she needs to find out where the £70 million shortfall has gone. She is a new broom who owes nothing to the old regime.”

The project, which includes union offices and a conference centre, was built under the tenure of Mr McCluskey, who said it was a “sensible investment of members’ money, resulting in a world-class facility that will return an income for our union for generations to come”.

Ms Graham ordered an independent inquiry into the investment after taking over, led by a QC. It is expected to give an update by the end of March.