Michael Shields, serving a 10-year sentence in a UK jail for the attempted murder of Bulgarian bartender Martin Georgiev in Varna in summer 2005, will not be able to be pardoned before May 2009 because a police review of his case, UK media reports said.

The Mirror reported that justice secretary Jack Straw’s order that Merseyside Police should investigate further has infuriated Shields' family.

Shields (22) was found guilty by Bulgarian courts of the attempted murder of Georgiev by repeatedly hitting the bartender with a paving slab. Appeals to the highest Bulgarian courts and to a European court to overturn his conviction failed.

Shields’s supporters won an application in a UK high court which ruled that as justice secretary, Straw could invoke the power of royal pardon to free him from the UK jail to which Shields was transferred under a bilateral custodial agreement between Bulgaria and the UK.

Website Click Liverpool said that Shields was "furious" when he learned from a local radio broadcast that he faces two months delay before a decision on his release.

Michael's father, Mike Shields, said: "Michael called me on the phone and he was absolutely fuming - both about the delay and the fact that he had to hear about it on the radio," the website said.

On February 25 2009, the BBC reported that convict Shields had spent his first night at home since being jailed in Bulgaria in 2005.

He was transferred to the UK in 2006 and is serving his sentence at Thorn Cross Prison in Warrington.

His father said: "He really enjoyed the time he had home and it was very emotional for all of us. His mum Maria and his sisters were in tears, we all were, but he was strong.

"We had a lovely sit down dinner and the family came to see him. But then we had to take him back to prison which was one of the hardest things I've ever had to do," the BBC quoted Shields senior as saying.