Senior Tory party sources intimated to supporters of the men, who belong to the Paris-based coalition movement, that they had been barred because Iran's charge d'affaires would be attending.
Yesterday, the Conservative peer Lord Moyne said it was outrageous to keep the opposition politicians out in favour of the Iranian diplomat in the light of continuing difficulties between the Government and Tehran, particularly the Iranian leadership's refusal to withdraw the fatwa against the author Salman Rushdie.
His dismay was echoed by Lord Avebury, chairman of the parliamentary human rights committee, who wrote to the Foreign Secretary, Douglas Hurd, expressing his indignation at the end of last month.
But a Tory party spokeswoman attempted to play down the row, saying that only those linked to embassies or parties affiliated to the International Democrat Union were invited to the conference.
Lord Moyne, however, said that neither Hedayat Matine-Daftari, chairman of the National Council of Resistance of Iran's Human Rights Committee, nor the group's UK representative, Bahman Etemad, had any difficulty gaining admission to the conferences held by Labour or the Liberal Democrats. Mr Matine-Daftari is believed to have sufficient support in Iran to propel him to a government post should the regime fall.
Mr Etemad said the invitation extended to the charge d'affaires, Gholamreza Ansari, was disgraceful and abhorrent, and would only encourage the regime to continue its repression of the Iranian people.
Lord Moyne added: 'It's absurdly short-sighted when you consider the influence these men could one day wield. Not unreasonably they feel a little insulted.'Reuse content