The peer's fourth wife, Editha, and fifth, Jinna, have staked rival claims that their sons should inherit the Moynihan fortune, which was founded on a business in the Philippines' sex industry.
But neither boy is now expected to accede to the Moynihan title after Sir Stephen Brown, president of the Family Division, ruled that the late baron forged divorce documents relating to his marriage to Editha, in a "thoroughly deliberate deception".
The fraudulent divorce means that Lord Moynihan's marriage to Jinna was bigamous, and that their son, Daniel, was illegitimate and not a legal heir. But neither can Editha's son, Andrew, inherit if results of DNA tests - which purport to show he was not the baron's son - are upheld.
The case now has to be considered by the Home Secretary, the Attorney General and Parliament's Committee of Privileges, but Colin Moynihan said yesterday: "It appears that the judgment ... makes it more, rather than less likely I will be the appropriate heir."
This will entitle him to a seat in the Lords, and a sum of around pounds 3,500 a year. The late baron's last two wives will now battle it out in court in the Philippines to decide who should inherit his Filipino fortune, said to be at least pounds 1.5m.
Sir Stephen said both Andrew, seven, and Daniel, five, were "victims of the wicked selfishness of Lord Moynihan".
In a 55-page judgment, Sir Stephen said the peer was a man "accomplished in fraud and indeed in forgery".
"He wished to obtain a divorce. He wished to do so even if his wife objected to it ...The inevitable consequences to all involved are serious. However, I have no doubt that I should set aside and declare null and void the decree absolute and the decree nisi."
With his wife, Gaynor, at his side, Colin Moynihan said the ruling was only a step forward, but he hoped the matter would be resolved by the autumn.
He added that if the title was his, he would accept it. "I shall take up my seat and be an active and strong supporter of the Conservative Government."
The third baron was a flamboyant figure, the black sheep of a family which had earned its title in 1922 through the distinguished service of his grandfather as the King's physician.
He fled to the Philippines in 1970 to avoid 57 drugs and tax-evasion charges.Reuse content