Sheridan Trial: Perjury case has cost the taxpayer £4.5m, says Sheridan's press officer

• Tommy Sheridan with wife Gail outside court

The figure was given as Tommy Sheridan opened his defence, by staying out of the witness box himself - he announced he would not be giving evidence - and calling an ally to testify about Freedom of Information requests which had secured details of expenditure.

Hugh Kerr, press officer for Sheridan's Solidarity party, was warned repeatedly by the judge, Lord Bracadale, that he was not to express personal opinions in his evidence.

However, he did suggest that upwards of 1.5m being spent on the police investigation, and the trial costing, he believed, an estimated 2m or 3m, was "an incredible waste".

Mr Kerr was prevented from adding more by the judge interrupting and repeating that he would not allow such comment.

Sheridan, 46, and his wife, Gail, also 46, are accused of committing perjury in 2006 in the former MSP's successful defamation action against the News of the World which had published allegations about his private life. Both deny the charge at the High Court in Glasgow.

Mr Kerr, 66, a semi-retired freelance journalist, was a founding member of the Scottish Socialist Party (SSP), and worked voluntarily in the Scottish Parliament for five years as Sheridan's press officer.

During the trial, Sheridan has alleged there was a plot against him by others within the SSP, and Mr Kerr confirmed yesterday there had been dissent and conflict which increased after the 2003 election, when the SSP gained six MSPs.

"The party began to be affected by people more interested in power and money," he said.

Mr Kerr named three of Sheridan's fellow MSPs, Carolyn Leckie, Rosie Kane and Frances Curran, as having formed "a divisive force in the party".

He added: "There were always people envious of the amount of publicity you (Sheridan] got … They clearly thought you were above your station.

"There was a lot of petty envy and jealousy towards you … They thought you were too big for your boots and ought to be taken down a peg."

Mr Kerr said he had submitted Freedom of Information requests to Lothian and Borders Police in connection with the perjury inquiry which had followed Sheridan's success in the civil litigation. He lived in Edinburgh and was concerned as a council taxpayer about "spending huge amounts of our money on what seemed to me to be an inappropriate investigation".

Referring to costs, he said: "The final figure we got to was around 1.5m which had been spent up to about a year ago. It is probably higher now. It excludes the cost of the Crown operation or the cost of the trial which, I gather, is estimated to be 2m or 3m, which seems to me an incredible waste."

One of the issues in the trial has been an alleged visit by Sheridan to a swingers' club in Manchester. A date suggested for the visit was the night of 27 September, 2002.

Alan Brown, 44, a civil servant, of Edinburgh, and also a member of the SSP, said he recalled meeting Sheridan on the Friday night of a Glasgow September weekend. He put the year as 2002, because it was a year in which his trade union had difficulties, and stayed in his mind.

Also, it had coincided with an SSP event in the unusual venue of the Centre for Contemporary Arts in Glasgow. Mr Brown was shown a programme for the event, and it was dated 27 September. He said he had seen Sheridan outside the venue, they chatted and Sheridan gave him a lift home to Hamilton.

Asked if he could be wrong about the meeting date, Mr Brown said: "I'm absolutely sure it was that Friday."

The trial continues next week.