A man who claims surgeons found a bullet from the Vietnam war in his leg has had his story called into question.

Major doubts have been cast on Robert Mitchell's story about the bullet, his battles in the Malay and Vietnam jungles – and even the authenticity of the Distinguished Service Medal he claims to have been awarded.

The story, which first appeared in the Dartmouth Chronicle and was then picked up by the Daily Mail, the Daily Express, the Times, the Sun and newspapers in Turkey, India and the US, has provoked a stream of comments questioning the legitimacy of Mr Mitchell's tale.

Naval historian Peter Singlehurst, who lives in Kent, saw the story in the national newspapers.

He said there was no record in the London Gazette of Mr Mitchell receiving a DSM; the involvement of British troops in Vietnam was 'slim to minimal'; and the South Vietnam clasp on the General Service Medal was only issued to Australians or 'Brits who had transferred to the Australian forces'.

An expert on military medals contacted the Chronicle and claimed: 'If his medal (the GSM) has the South Vietnam clasp, then I am even more suspicious because that is mega rare and only awarded to a handful of Australians.

'The Royal Warrant of June 8, 1968 – repeated in the Australia Gazette No 60 of 1968 – stated that it was for Australian troops only – serving in Vietnam in the period December 24, 1962. to May 29, 1964, and only 68 men qualified, all members of the Australian Army Training Team Vietnam (AATTV) who were mainly special forces guys training the locals during operational missions.'

The expert added: 'The number of Distinguished Service Medals awarded since the Second World War is tiny and this chap is not listed amongst them. Every award has to be published in the London Gazette – even the covert operations, SAS ones for Ulster, Afghanistan, etc, sometimes 10 years late, but published all the same – and nobody of that name is amongst them.'

Despite the comments, Mr Mitchell was adamant that his story still stood up.

He said he had been presented with his medals in the early 1970s while he was stationed at the Britannia Royal Naval College in Dartmouth and still receiving medical treatment for his combat wounds.

He said he had been searching for the paper records of the medals but had been unable to find them and thought they may have been lost in a move to his current home or destroyed following a relatively recent rat infestation.

'We had to throw stuff out that had got chewed up and there were sacks of it,' he said.

But today the 63-year-old secretary of the Dartmouth branch of the Royal Naval Association was standing by his story of derring-do while he was a Royal Naval Commando fighting alongside American forces in Vietnam.

'I have no problem with what people say. I stand by everything that I have said,' he declared at his home in Britannia Avenue, Dartmouth.

Mr Mitchell added: 'Are they saying my whole life is a lie? It is upsetting.

'I never wanted any of this publicity in the first place.'

Mr Mitchell claims he was serving in the Royal Navy when he was wounded while in action on the Malay- Thai border in 1970 and then wounded again fighting with US forces in Vietnam after being teamed up with an Australian unit in 1971.

He claimed that earlier this year he went into hospital for a hernia operation and when he was operated on the surgeon found the bullet which was then cleaned up and presented to him.

Tellingly, a spokesman for Torbay Hospital, where the operation was carried out, has issued a short statement saying: 'We can confirm that Mr Mitchell was in our care recently for a routine hernia operation with no unusual circumstances.'

The DSM roll of honour:

The following Distinguished Service Medals have been awarded since the Second World War, according to the London Gazette, which records honours:

Kirwin, Patrick John Dennis: serving with the Royal Navy during the Brunei Revolt; date awarded, May 31, 1963.

Boylan, Lance William: Royal Navy, Malaysia (Borneo), December 14, 1965.

Taylor, Charles Kenneth: Royal New Zealand Navy, Malaysia (Borneo), December 13, 1966.

Kember, Phillip Charles: Royal Australian Navy, Vietnam, February 2, 1968.

Young, William John: Royal Australian Navy, Vietnam, July 7, 1968.

Sculley, Graham Henry; Royal Australian Navy, Vietnam, February 6, 1969.

Aldenhoven, John Adrian: Royal Australian Navy, Vietnam, June 24, 1971.

Since then, in the 1980s, 12 British servicemen received the DSM for their part in the Falklands War.

In the early 1990s, two servicemen were awarded the DSM for actions in the Gulf War.