Retired soldier Dennis Hutchings has claimed that the Ministry of Defence (MOD) has refused to back him in his bid to stop "discriminatory" prosecutions of Northern Ireland veterans.
Mr Hutchings' non-jury criminal trial for the attempted murder and grievous bodily harm with intent of John Pat Cunningham in Armagh in June 1974 will begin on March 9. Mr Cunningham, who had learning difficulties, died after being shot in the back as he ran away from an army patrol.
Previous investigations concluded that no action should be taken against Mr Hutchings.
He denies the charge and is taking legal action against the Northern Ireland Office (NIO) "to end discriminatory prosecution of veterans in Northern Ieland".
An MOD spokesperson said they could not support Mr Hutchings legal challenge as it "would see the Government using taxpayer's money to pay for legal action against itself".
The case, alongside that of Soldier F, charged with two murders on Bloody Sunday, has attracted widespread attention, with campaigners claiming former soldiers should not face prosecution for carrying out their duties.
Prime Minister Boris Johnson has pledged to end "vexatious" cases against former Northern Ireland veterans, making it part of the Conservative Party's 2019 General Election manifesto.
In a statement issued through his solicitors McCue & Partners Mr Hutchings said that any legislation introduced by the Government will be "too late" with his trial set to begin next week.
The 78-yar-old former member of the Life Guards regiment said he had "no faith" effective legislation would be introduced to protect veterans "given competing political agendas between Westminster and Stormont".
Mr Hutchings claimed the Government had refused repeated requests to meet with him to explain what the proposed legislation would entail and to try and see a resolution without legal action.
"Following the refusal from the MOD to back my challenge against the NIO, I feel totally let down yet again by the government," he said.
"Any legislation, if it comes at all, will be too late for me but I will continue the fight to stop this political and vengeful vendetta against service veterans who were only serving their country having been sent by politicians to a job, which was to protect the public.
"The time is now for the politicians to hang their heads in shame for how they are treating the veterans of this country.”
Matthew Jury from McCue & Partners said the NIO had funded a case against itself as recently as 2017.
"With proper checks and balances, it’s not unreasonable to expect that the Government should back a case against one of its departments when that department is facing allegations of facilitating the vexatious prosecution of British Army veterans, something that is clearly against the public interest.
"The fact is, any legislation will now come too late, if it comes at all, to protect Mr Hutchings. Nonetheless, Mr Hutchings intends to continue his campaign to ensure that other veterans are spared his ordeal.”
A UK Government spokesperson said they remained committed to ending the prosecution of veterans.
"The Prime Minister has been clear we will end the vexatious prosecutions of veterans, including bringing forward legislation to address the legacy of the past in Northern Ireland.
“As the PM has said, we will implement the Stormont House agreement in such a way as to provide certainty for veterans and justice for victims.”
It is understood the Government is still considering responses to a public consultation on dealing with the legacy of the Troubles.