The contractor who allegedly overcharged Unite by £30m to build a new hotel and conference centre arranged flights and football tickets for the union’s former General Secretary Len McCluskey, according to an internal report.

A Unite investigation led by construction lawyer Martin Bowdery KC into the controversial scheme in Birmingham claims the job was awarded with no competitive tender to contractors who were “good friends” of McCluskey.

The building was under construction from 2016-20 and cost over £110m. It was later valued at £38m.

The report stated that the original contract gave the builder an “officially agreed £12.5% profit mark-up” before extra costs started to mount up.

The cost of preliminary items like scaffolding and machinery jumped from £11.9m to £22.4m which the report “could not identify any reasons for.”

Other increases identified in the investigation included the cost of “holes through blockwork and the like” rising from an original estimate of £91,000 to £1.28m.

The cost of rainscreen cladding also rose 375% to £3.3m.

McCluskey’s lawyers told the BBC he paid for his own travel in full, and, to his recollection, always paid the cost of his football tickets.