• Tommy Sheridan and his wife, Gail, after he was found guilty earlier in the week. Picture: Getty
Sheridan, found guilty at the High Court in Glasgow last week, is to claim "key witnesses" were blocked from speaking at the trial and that e-mails were withheld from his defence lawyers.
The former MSP was told by the trial judge Lord Bracadale to "expect to begin a prison sentence" when he returns for sentencing on January 26.
A source close to the Sheridan camp revealed that the left winger's legal team will start to put together an appeal against the conviction within a matter of days, once "Tommy has had a few days of Christmas with his family".
Sheridan was found guilty of five counts of perjury relating to evidence he gave in his civil court battle against the newspaper The News of The World.
Sources said his appeal will focus on the "withholding of crucial e-mails" sent between the Scottish News of the World and private investigator Glenn Mulcaire. Mulcaire was jailed in 2007 after it was found he was hacking into the phones of celebrities and other prominent people and selling the information to the newspaper.
Scotland on Sunday spoke to Labour MP and former minister Tom Watson, a senior member of a Commons committee probing the hacking allegations, who has now lodged a complaint with the UK's Information Commissioner over what he says was a "highly suspicious" claim at Sheridan's trial by Scottish NoW editor Bob Bird that e-mails sent about the newspaper's investigation into the former SSP leader had been lost.
Bird claimed during the court hearing that "many e-mails had been lost when they were being moved to an archive in India" sparking the complaint from Watson that the loss of data was in breach of the Data Protection Act and that the Information Commissioner must "get to the truth."
The source close to Sheridan also said that the appeal would also centre on the fact that defence lawyers were stopped from quizzing Mulcaire during Sheridan's trail, after he was excused from giving evidence due to a doctor's note.
Sheridan's defence team will argue that the absence of information about the availability of the e-mails from the NoW investigation and the lack of an opportunity to question Mulcaire may have prevented critical evidence being revealed that could have cast "reasonable doubt" over Sheridan's guilt.
The appeal will also cite the trial judge Lord Bracadale's decision to stop Scottish comic Des McLean, who previously impersonated Sheridan on the radio, from giving evidence.
A crucial piece of evidence in the trial was a video on which Sheridan was heard admitting he had attended sex clubs, but not seen. Sheridan denied the voice heard was his and said there was no scientific evidence led to prove that it was.His legal team believe that had McLean been allowed to show his impersonation skills in court it would have cast doubt on the authenticity of the tape.
His lawyers will also say that excusing former escort girl Fiona McGuire from giving evidence at Sheridan's trial on the grounds of illness counted heavily against the former Glasgow list MSP. McGuire famously told a court she had a five-in-a-bed orgy with Sheridan at an Aberdeen hotel.
Another key plank of the appeal will be that judge Lord Bracadale "wrongly instructed" the jury at Sheridan's trial, just before members retired to deliberate on their verdict. However, the source close to Sheridan would not discuss details of that part of the planned appeal until Sheridan had been able to talk at length about it with his lawyers.
The source told Scotland on Sunday that the former SSP frontman was "upbeat" and "philosophical" following his conviction and that he would be able to survive a lengthy prison sentence.
He said: "Tommy will be popular in jail and most prisoners will be sympathetic to him."