The father of an SAS sniper jailed for illegally possessing a gun has told Sky News his son was bullied into pleading guilty at a court martial.
Humphrey Nightingale said: "We knew Danny was not guilty but the judge made it quite clear that if he did not plead guilty he would be sent to a civilian jail for a minimum of five years.
"Our hands were tied and we had no other option - Danny has a lovely wife and a young family.
"We expected a lenient sentence - maybe suspended - but instead he was sentenced to 18 months."
Sgt Danny Nightingale, a father-of-two who served in Iraq and Afghanistan, is at the Military Corrective Training Centre in Colchester, Essex, after admitting possessing a prohibited firearm and ammunition.
The gun, a 9mm Glock pistol, was a gift from Iraqi soldiers he had been training. It had been packed up and returned to him by colleagues in Iraq, after he had to leave the country in a hurry to help organise the funeral of two friends killed in action.
Sgt Nightingale suffers medical problems which affect his memory and said he did not remember having the weapon.
The controversial case has sparked outrage from SAS veterans. MPs will debate the case this evening.
Mr Nightingale said his son was "100% innocent" and urged Prime Minister David Cameron to apply "any pressure he can".
Lawyers for Sgt Nightingale say they will lodge an appeal against his conviction and sentence later this week, as well as applying for bail.
His wife Sally visited him on Monday for the first time since he was sentenced two weeks ago.
Mrs Nightingale said her husband was struggling with being locked up for 16 hours a day.
"Danny's an outdoor person; he never sits still and it's very hard for him to be in there," she said, "but with all the support behind him, that will see him through."
An MP supporting Sgt Nightingale said visiting the soldier had "filled him with determination" to get justice.
Julian Brazier, MP for Canterbury and Whitstable, said: "It was humbling in a way to feel that such a guy, who has given so many years service could have been brought so low by a system of which I am part, the legislature.
"It filled me with a determination that we have to get justice for this guy."