The head of the Moruroa e tatou veterans organisation in French Polynesia, Roland Oldham, says allowing access to the atoll would quell claims and counterclaims about work on the atoll.
The ruling Tavini Huiraatira says it has confirmation from various sources that work has been underway for several weeks to construct a bunkerlike building.
The French High Commission has denied this.
However Mr Oldham says access to the atoll is being denied.
"We have met workers, people who have contracts to work on Moruroa about the construction planning to happen in Moruroa. And it's very hard for us to get workers as a witness because it's very simple, they lose their job."
Roland Oldham says a bid to visit again will be made through a French Senator which Paris will find hard to reject.