Mrs Shields added: "Michael is suffering in jail, he shouldn't be there.
"He has lost a lot of weight and he looks pale."
Graham Sankey from Anfield, has claimed responsibility for the attack in a statement to a Merseyside solicitor, but the evidence was rejected at Mr Shields' original trial in Varna.
Appeal court judges refused to reduce the sentence but did agree to decrease the fine.
Michael's legal team are now preparing to lodge a further appeal with the Court of Cassation in Bulgaria.
David Kirwan, Graham Sankey's solicitor, said: "Graham Sankey is neither a coward nor scared of taking the blame for any crime he may have committed.
