Alan Costello, who owns A T Derbyshire chemists in Fingerpost, was last seen exploring a huge shipwreck in the Red Sea on May 20.

The 52-year-old father, of Moss Bank, St Helens, had been on a week-long holiday with members from Northern Union, a local diving club. He had been part of a team of four divers when he swam off with his diving buddy to investigate more of the ship.

They suddenly became disorientated in the engine room and both Alan, an experienced diver, and his pal began kicking causing sediment from the seabed to blur their vision. His diving buddy made it to the surface but there was no sign of Alan.

He raised the alarm and the authorities have organised an extensive air and sea search in the vicinity and a number of local dive operators have joined the search of the wreck.

Alan's family and friends are desperate for information. They have posted various pleas for help on local diving websites in the hope that he might be found.

Ron Mahoney, a close family friend, said: "We are devastated and we are hoping that he might have made it to one of the 50 small islands in the region.

"He is an experienced diver and he has dived all over the world. Alan has explored the Red Sea before and it is popular with thousands of diving enthusiasts."

The team of divers had been exploring the wreck of the Rosalie Moller near Hurghada. The rest of Alan's diving companions returned to St Helens on Saturday after helping with the continuing rescue effort.

The Foreign Office and the Egyptian authorities are liaising with the family.

A Foreign Office spokeswoman said: "We can confirm that a British citizen went missing off the coast of Egypt and we are working with the local authorities there to do all we can to find him.

"We are also liaising with the family and offering them support at this difficult time."