The archaeologist who discovered a silver cross exposed by scientists last week as a Roman “hoax” says he is convinced that the find is genuine.

Quentin Hutchinson has remained silent since he found the early Christian Chi-Rho amulet while excavating a 4th-century grave near the Somerset town of Shepton Mallet in 1990.

It was initially regarded as the earliest evidence of a Christian burial in Britain and was hailed as one of the archaeological finds of the century. But after tests by experts at Liverpool University, which concluded that the silver was of 19th-century origin, it has now emerged that doubts about its authenticity were voiced almost from the moment it was found.

Mr Hutchinson, 46, has never before spoken publicly about his discovery of the tiny cross on Sunday, July 15, 1990. But now he says that it has ruined his life and he wishes that he had never found it.

His integrity was called into question soon after the find, and the suspicion that he had planted the cross himself ended his professional career.

He denies playing any part in a hoax and maintains that it would have been impossible for anyone to plant the amulet without disturbing the soil. In the absence of such evidence, he is convinced that the cross could only have come to be underneath the right femur of the skeleton of a middle-aged man, possibly a priest, if it had been buried with its owner more than 1,600 years ago. He believes that the experts must reconsider because the find may yet prove to be of great importance.

In the summer of 1990, Mr Hutchinson, then 28, had been an archaeologist for four years and was a member of Birmingham University’s Field Archeology Unit. It had been asked to conduct a dig at the site of a proposed £6 million warehouse development. What they uncovered, beside the Fosse Way was evidence of a large Romano-British settlement, with roadside buildings, workshops, agricultural enclosures and industrial workings.

There were also three 4th-century cemeteries, one of which – where the graves lay east to west – was thought to be Christian. Mr Hutchinson was asked to complete the excavation of one grave, which had been left by a colleague with the upper half of the skeleton uncovered but the lower half still hidden beneath compacted soil.

“I began lowering the grave fill. You can always tell, from subtle differences in colour and texture, if there has been a disturbance. In this case, the soil was very clean, very compact. It did not look to have been disturbed in any way. The site director [Peter Leach] had already looked at it with me. There was absolutely nothing to suggest that it had been tampered with.”

When Mr Hutchinson reached the upper right leg bone, he noticed a fleck of black and a bead, embedded in the soil next to the bone. He gently removed a fist-sized clod of earth surrounding the object and lifted it out.He found himself holding a small silver cross, 45mm long, and 39mm wide. The bead had been the tip of one of its four points. Heart racing, he hurried to Mr Leach, who wiped the remaining soil from the small disc at its centre.

This revealed the Chi-Rho marking, an early Christian symbol formed by superimposing the first two letters, X and P, of the Greek word Christos, “the anointed one”. He said: “I thought, ‘Oh my God, what have I found?’ It was a once-in-a-lifetime moment. Peter Leach said that nothing like it had ever been found in Britain. It was incredibly exciting.”

Within days, word spread of the amazing find and Shepton Mallet seemed destined for fame as one of Britain’s earliest centres of Christian belief. Mr Hutchinson left Britain on a short holiday two months later. When he came back, his world fell apart.

“My director called me into his officeand told me that he had been asked by the British Museum to question my professional conduct because they were convinced that the amulet was a modern hoax.”

Mr Hutchinson was asked if he had planted it. He angrily denied the accusation. The find remained, officially, genuine until last week’s tests but passion for archaeology – and trust in Britain’s archaeological establishment – left its finder many years ago.

Shattered by the suspicions surrounding him, he resigned from the Birmingham team in 1991 and left the profession in 2000. He has subsequently worked as a teacher, in a post office and in a supermarket. He now wants a gathering of experts to thrash out the controversy.

“I’m not an expert on Roman silver, so in that sense I can’t say whether the amulet is genuine, but what I do know is that it came out of an untouched grave. My suspicion is that the real problem is that the amulet is unique.

“Because it doesn’t fit their understanding of the period, they are determined to believe that it cannot be genuine. The truth is I wish I’d never found it, because it ruined my life.”