Joan Guzman is moving up a weight

The unbeaten Dominican, who was the mandatory challenger, had signed a contract to take on the Glaswegian.

But Guzman has now declared that he is moving up to super featherweight, leaving Harrison seeking a replacement.

The Scot said: "I said all along that I would beat Guzman. It's a shame that he didn't have the heart to face me."

Harrison added: "Now I'm more fired up more than ever before and I feel sorry for whoever gets in the ring with me on 20 May."

It's a real liberty on the part of Guzman Promoter Frank Warren

Harrison's promoter Frank Warren was scathing about former WBO super bantamweight champion Guzman, who has signed to fight former lightweight world champion Javier Jauregui in Las Vegas on 6 May.

"After talks with Guzman's camp, they made it clear that Joan has no intention of facing Harrison," said Warren.

"To say I am disappointed, especially when we had a signed contract for the fight, is an understatement.

"It's a real liberty on the part of Guzman and I think he swallowed it, plain and simple.

"All the talk from him has been about what he was going to do to Harrison, but I think it was beginning to dawn on him that Scott really wanted the fight - and to give him a hiding.

"And isn't it ironic that, having constantly questioned Harrison's ability to make the weight - unlike Guzman, has never failed on the scales at a weigh-in - it turns out that he's got the problem."

Warren and match-maker Dean Powell are now working hard to find a replacement for Guzman and are confident of announcing a top-rated opponent within the next few days.

As well as Harrison's WBO title defence, the show will feature a welterweight match-up between WBU champion and local hero Eamonn Magee and challenger Takaloo.

Olympic silver medallist Amir Khan will have his seventh professional fight, taking on former European lightweight title challenger Laszlo Komjathi.