A former spokesman for a campaign to defend left-winger Tommy Sheridan performed at a Scottish Labour rally attended by Jeremy Corbyn and Richard Leonard.

Poet Jim Monaghan, who was also a defence witness in Sheridan’s perjury trial, was one of the warm-up acts at the high-profile event in Glasgow earlier this month.

Tom Harris, a former Labour MP in the city, said: “Tommy Sheridan is one of the most divisive people in Scottish politics. There should be alarm bells ringing if one of the individuals who offered him strong support is now one of Richard Leonard’s strongest supporters.”

In November, Corbyn and Leonard came together for the first time since the Central Scotland MSP was crowned leader of Scottish Labour.

Following a joint meeting of the national executive committee and the Scottish party’s governing body, a rally took place in Glasgow’s east end.

More than 200 members joined the two leaders at an event described by general secretary Brian Roy as a “fantastic night”.

Roy wrote in an email that “great poetry” had been provided by Monaghan, who gave a reading ahead of the speeches by the politicians.

However, a Labour member told this newspaper he was unhappy with Monaghan’s appearance due to the support he offered Sheridan during the former MSP’s battle against the now-defunct News of the World and the legal authorities.

In 2006, Sheridan successfully sued the newspaper’s publishers over claims he was a swinger and adulterer, but four years later he was convicted of perjury in the first trial and given a three-year jail sentence.

Monaghan helped form the Defend Tommy Sheridan Campaign after Lothian and Borders police launched an investigation into the evidence given in the first trial and he played a role in the group until 2010.

Ahead of the perjury trial, a statement was released by the group in Monaghan’s name: "This disgraceful waste of public funds and resources on behalf of Murdoch's business interests has to end now. Gail and Tommy are being victimised while the Police and Crown Office are facing cuts."

A key issue in the perjury case was conflicting evidence on whether Sheridan visited the Cupid’s sex club in Manchester on September 27th, 2002.

Some witnesses alleged that the former MSP had attended, but Monaghan told the jury he saw Sheridan at an event in Glasgow on the night in question. In the end, the jury ruled that Mr Sheridan had gone to the club.

Monaghan later embarked on a book project - ‘A Parcel o' Rogues – The Tommy Sheridan Conspiracy’ - and he set up a blog to post updates.

He is believed to have joined Labour in 2010 and his Twitter biography describes him as a poet, writer, researcher and trust administrator at Govanhill Baths in Glasgow.

Harris said: “Labour is now seen as a welcoming place for many people on the hard-Left.”

Monaghan said he believed it had been the seventh Labour event he had appeared at in recent years as a poet.

He also said he had been employed by the Labour group on East Ayrshire council to carry out press duties in around 2011.

He added: “I actually performed at the Labour parliamentary Christmas party a couple of years ago, in the Scottish Parliament.”

Asked if he still believed Sheridan was the victim of a conspiracy, Monaghan said: “Yes, absolutely.”

A Scottish Labour spokesman said: “Jim Monaghan is a well-known and popular poet who attended the Rally for Real Change to perform his poetry.”