Around 1,000 British servicemen who took part in atomic tests in the 1950s won the right to sue the government on Friday for health problems they blame on nuclear radiation.
The veterans, who are seeking to launch a multi-million pound group compensation claim, took part in British nuclear tests in Australia and the Pacific Ocean.
The Ministry of Defence, which denies negligence, had sought to throw out the veterans' action at the High Court in London, arguing that it was launched outside a legal time limit.
But on Friday, Judge David Foskett rejected the MoD's submission and gave the veterans the green light to proceed with their claim, the Press Association reported.
"All things being equal, a veteran who believes that he has an illness, injury or disability attributable to his presence at the tests whose case is supported by apparently reputable scientific and medical evidence, should be entitled to his day in court," Foskett said in a written judgment.
Douglas Hern, litigation secretary of the British Nuclear Test Veterans Association, said he hoped the government would now negotiate a settlement rather than appeal the ruling.
Hern, 73, blames the death of his 13-year-old daughter from cancer on his radiation exposure. He said that if the litigation continued without settlement many ex-servicemen would not live to see the eventual outcome.
The Liberal Democrats hailed the court ruling and called on the ministry to end its "penny-pinching" treatment.
"Other countries from the US to China compensated their test veterans years ago," said Lib Dem Defence Spokesman Nick Harvey. "It is scandalous that the government has continued to shirk its moral responsibilities for so long."
The ministry said it was disappointed by the ruling and would review the full judgment before deciding how to proceed.