The IRB released a statement today confirming there would be no re-vote for the 2011 hosting rights which New Zealand secured ahead of hot favourites Japan in Dublin in November.
"(The IRB) takes exception to any suggestion that the vote was not carried out in a proper and professional manner," the statement said.
London's Sunday Times yesterday reported that the Asian Rugby Football Union (ARFU) had threatened legal action unless the IRB annuls the vote made by its ruling council in Dublin.
Sunday Times rugby correspondent Stephen Jones reported that the ARFU, of which the Japan Rugby Union is a member, had petitioned the IRB asking for a new vote on the grounds that the previous ballot lacked transparency because the way council members cast their votes was not disclosed.
English lawyers Addleshaw Goddard, acting on behalf of the ARFU, said in a letter to the IRB that the voting secrecy breached its constitution.
The IRB today said the voting process and procedure was approved by the directors of Rugby World Cup Limited and the IRB council, and the vote itself was verified by independent auditors from Pricewaterhouse Coopers.
"A letter containing various unsubstantiated and unfounded allegations has been sent to the IRB from an English firm of solicitors purporting to act on behalf of the ARFU and was printed in part in an English newspaper," the IRB said.
"The democratically elected officials of the ARFU have informed the IRB that the letter should not have been sent as it does not represent the views of ARFU and that the person who it seems engaged the solicitors did not have the constitutional authority to do so.
"The Secretary General of ARFU has written to the solicitors stating that they must cease and desist purporting to act for and on behalf of the Asian Rugby Football Union."
New Zealand Rugby Union (NZRU) chief executive Chris Moller rejected the claims in the Sunday Times article.
"In a word they're nonsense, in two words they're complete nonsense, and in three words they're absolutely complete nonsense," Moller said.
Moller said the assertion that hosting the tournament in New Zealand would harm the sport was a repeat of "stories from the northern hemisphere" ever since the IRB decision.
"Most of the northern hemisphere media had completely written us off and they're embarrassed by the fact we have achieved what is quite a coup, and frankly it's time to move on and focus on why New Zealand was successful.
"We had a compelling case and that is why we succeeded. There was no horse-trading, there were no deals done and any suggestions to the contrary are scurrilous and frankly very disappointing."