Mr Hain said no future British Premier would devote the same amount of energy as Mr Blair to making Stormont work as he urged them to meet the November 24 deadline for an agreement.
The comments carry extra weight as Mr Hain is known to be an ally of Mr Blair’s likely successor Gordon Brown.
Mr Blair has announced he will resign as Prime Minister within 12 months, but many political commentators expect him to be gone early next year.
At a meeting with foreign minister Dermot Ahern in Dundalk, Mr Hain praised Mr Blair’s “forensic attention” to the North and said a future Premier may not be able to give the same focus to the problem due to competing world events.
Mr Hain added no successor could match Mr Blair’s level of expertise on the North as he predicted a lasting settlement could banish terrorism from Ireland forever.
Mr Hain praised the achievements of Taoiseach Bertie Ahern and Mr Blair as he cranked-up pressure for a November deal on creating a cross-community Executive.
“There is nobody else — no successor who can do the type of job that the Taoiseach has done and the Prime Minister has done.
“They have the strategic brilliance to be able to conclude all of these.
“It’s absolutely crucial that all the parties take advantage of their detailed knowledge and attention.
“I’m not sure you will get a British Prime Minister who will give this kind of forensic, detailed attention to solving these problems because the world will move on after November 24,” the Northern Secretary said.
At a meeting coinciding with the fifth anniversary of the 9/11 attacks, Mr Hain indicated the world would move on after November and this was a rare opportunity to finally take the gun out of Irish politics.
“Life will move on from the elected politicians of Northern Ireland.
“The MLAs will forfeit their role to be politically significant in Northern
Ireland and to represent their communities,” Mr Hain said.
The warning came as the proposed merger in the shadow Stormont Assembly between the Ulster Unionists (UUP) and the Progressive Unionists (PUP) — a party aligned to the loyalist paramilitary Ulster Volunteer Force (UVF), was declared a breach of the rules.
Eileen Bell, Speaker at the Assembly, revealed after legal discussions that the UUP’s grouping did not have proper party characteristics.