Former Labour MP Dan Norris, the elected mayor for the West of England Combined Authority (WECA), approved the spending for the advertisement to promote a free bus travel scheme around the region.

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It was never shown publicly after the local authority's interim chief executive learned about it and stopped it - fearing it was personally promoting the mayor over the scheme.

However, a report into the matter said "£10,000 of public funds were nevertheless unlawfully spent wrapping the bus".

The wrap featured two pictures of the mayor and his dog, called Angel, on either side of the bus and a further image of Mr Norris on the rear of the vehicle. It was designed to promote a scheme giving people free travel during the month of their birthday.

The report said while there is no problem in principle with the promotion of the scheme, or associating the metro mayor with it - the objection lay with the fact the images were far too big.

One image was three metres high, the second two metres high and the third one metre high.

The report stated the "imagery associated with the metro mayor should be merely 'incidental' to the main purpose of the spending, which is to promote the bus service improvement plan".

"Instead, the wrap appears to explicitly seek to affect public support of the metro mayor," the report noted.

"It seems that the promotion of the bus service improvement plan is incidental to the promotion of the metro mayor himself."

It added that the bus wrap is "reminiscent of political campaign buses which exist to serve the explicit purpose of seeking to influence voters".

A further cause for concern was the fact Mr Norris regularly used images with his dog "as a personal brand or motif" on his political campaigning platforms.

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The report said: "In light of these factors, it is difficult to come to any conclusion other than that the effect of the decision taken on or around April 24 2023 was, in reality, to incur expenditure of £10,000 of public funds not just to launch the birthday fares package initiative, but to promote or seek to affect public support for the metro mayor personally, and this is the conclusion which both the interim monitoring officer and the Section 73 officer have reached."

The WECA is holding an emergency meeting on December 1 to discuss the contents of the report.

The committee will be asked whether it agrees with the findings of the report and also decide "what action, if any, it proposes to take in consequence".

Committee members are the leaders of the South Gloucestershire and Bath & North East Somerset councils, Bristol's directly-elected mayor and Mr Norris, although he will not be present when the report is discussed.

Mr Norris was elected as the mayor in 2021 representing the Labour Party having previously been an MP for Wansdyke between 1997 and 2010.