In 2009 the ministry contested the right of the veterans to sue, claiming they had waited too long and had exceeded the statute of limitations.
At a hearing in the High Court in London, Justice David Foskett ruled in favour of the veterans' court action being able to proceed but since then matters have see-sawed.
The ministry appealed and won and then Supreme Court judges ruled 4-3 in favour of the ministry.
Lawyers for the claimants have not abandoned the class action, but it has become deadlocked.
With the death of Mr Harris, the Wairarapa claimants are down to one as Mr Ferguson has also died.
Mr Harris, along with other veterans of the nuclear test series code-named Operation Grapple, received only a special services medal "for hazardous duty".
At the time he received the medal, Mr Harris described being a witness to the bomb tests.
"We were at ground zero - as it was called - and after the explosions we steamed right through the radiation cloud," he said.
The bombs tested at Christmas Island were plated with depleted uranium, which veterans had not known about, and was described by Mr Harris as being "deadly stuff".
Mr Harris is survived by his wife Margaret and three adult children.
A funeral service will be held for him at 11am today at the Wairarapa Services and Citizens Club.