Defence Secretary John Healey has launched an investigation into whether there are long lost or hidden documents that reveal military chiefs secretly monitored the health of men who witnessed nuclear bomb tests in the 1950s.
John Healey told MPs that while "nothing is being withheld", officials would carry out a "detailed dig" amid concerns from the surviving veterans.
The pledge comes after the BBC screened a special documentary on Wednesday into allegations that there has been a decades-long cover-up of how the nuclear testing programme harmed personnel.
Alan Owen, one of the leaders of the men's campaign said the decision was a "brilliant" step forward after years of battles for answers.
Survivors in their 80s say many of them and their children have suffered cancers, genetic defects and other illnesses that must be linked to radioactive fall-out.
Similar claims have been made by indigenous communities in Australia where many of the tests were conducted.
For decades, successive governments have denied there was a secret monitoring programme - but the veterans say recently declassified files support their memories of medical staff taking blood and urine samples.
Speaking to Parliament's Defence Committee, Mr Healey said the investigation would not be straight-forward and records may have been lost.
But he said he wanted to make sure that everything that was available was disclosed to the men.
"Nothing is being withheld. We're doing a detailed dig into what may be held, but we've not been aware of it," he said.
"Exercises like this in any part of government often do throw up material and documentation that may have been archived.
"I take our duty to the nuclear test veterans very seriously. I was with Keir Starmer when he was the first party leader to meet with the nuclear test veterans.
"And he gave those veterans his, as I did, our undertaking that we would get to the bottom of the concerns that they had.
"If there are documents that the government holds in any part of the system, then we will release them."
Alan Owen, of Labrats, the men's campaign, welcomed the minister's pledge.
"I think it is positive. We have had a meeting with the Office for Veterans' Affairs. We need answers and if John Healey can deliver them, then brilliant."
The veterans and their lawyers have proposed the government launches a limited tribunal to establish whether documents were hidden, as an alternative to legal action.
But Mr Healey said a judge-led process could take years to get answers.
"I've met some of these aging and some ailing nuclear test veterans and I have just enormous respect for the campaign that they've run and share their frustrated anguish," he said.
"The importance is that we get to the bottom and try and answer the questions they've got."