Michael Shields' family claim he is a scapegoat

Stephen Jakobi, of pressure group Fair Trials Abroad, met the Bulgarian ambassador, Lachezav Matev, in London.

He said he got the "utmost goodwill" of the Bulgarian government and that it would push to reopen the case.

Michael Shields, 18, was jailed for attacking a barman, despite another man admitting he carried out the attack.

A confession made by Graham Sankey, 20, of Anfield, to his solicitor saying he assaulted waiter Martin Georgiev was not accepted by the Bulgarian court.

I am going to fight with every breath in my body, even if it's my last breath Michael Shields Snr

Mr Georgiev, 25, suffered a fractured skull when he was assaulted after asking a group of Liverpool supporters to quieten down at a fast food restaurant in Varna.

Shield's legal team said on Thursday that they could get his sentence halved. They are planning two appeals - one to cut Shields' sentence and one to free him on bail.

"The lawyer expects to get the sentence reduced to half because they can present new evidence," said interpreter Amelia Patrova.

"But we can't overturn it unless the real perpetrator comes forward."

Meanwhile, Stephen Jakobi met the Bulgarian ambassador on Thursday.

He said: "We have made a breakthrough. It may not sound like a huge breakthrough but it is the start of something very important.

"We realised the only way out was to get some sort of investigation initiated in Bulgaria. There is no way we can acquire proper evidence unless the Bulgarians start it."

Martin Georgiev's may have permanent brain damage

Once an investigation is under way in Bulgaria, an arrest warrant could be issued for Mr Sankey and extradition proceedings begun.

Mr Jakobi appealed for Mr Sankey to hand himself in to Bulgarian officials to speed up the process.

Shields' father, also called Michael, and sister Laura flew to Bulgaria from their home in Edge Hill in Liverpool on Thursday morning.

"I am not going to give up. I am going to fight with every breath in my body, even if it's my last breath," Mr Shields said.

"Even if it puts me six-foot under I have promised I will get my boy home to his mother."