Perhaps Dr Yazdi's revolutionary credentials give him some protection. He is a former member of the Revolutionary Council and Deputy Prime Minister, who served in the first Cabinet of Mehdi Bazargan, Ayatollah Khomeini's one-time special envoy to Iran's rebellious provinces, and an ex-member of the Iranian parliament. Dr Yazdi, white-bearded and bespectacled, looks more like a country doctor than the leader of the illegal opposition Freedom Party. Indeed, he is a pharmacologist, specialising in molecular genetics. But he clearly sees himself as the voice of the "silent majority" - a majority he believes should be demanding political liberty.
"Politically and economically, we are experiencing a very severe crisis in our country today and we feel that people must show concern and come forward and participate fully in the parliamentary elections next month," he says. "One part of our crisis is that no opposition party is allowed or tolerated in Iran. You cannot call this a one-party state, because there is no party."
Dr Tazdi has only been in prison once, after the 1953 military coup d'etat, but he seems unafraid of what the future might hold for him; maybe the government has too many other problems to worry about just now than arresting a 63-year-old pharmacologist.
"The two major aspects of the revolution were the basic rights and liberties of the people, and the political and economic independence of the country. Both have been the concern of freedom fighters in Iran since the 1908 Constitution. Political liberties was one of the major goals of our revolution - and it's unfortunate that this has not been fulfilled. The political liberties that we are demanding are only a vehicle. The moment the authorities accept the freedom of political parties which is provided for under Chapter 3 of our Constitution, the political atmosphere will be ready for a serious debate on the deeds of the government."
Dr Yazdi knows very well that even those who were prepared to die in Iran's bloodbath of a war with Iraq are now deeply discontented with the regime. "Many young people who fought at the front are observing widespread corruption among the government. They are very bitter."He added: ''From what the Revolutionary Guards are saying in their newspapers, I assume this is also their concern."
The government, Dr Yazdi says, is selling gold coins on the market. "Coining gold is exclusively the government's job so the government are the people creating the inflation ... where are all these dollars coming from that go into the black market? Many experts say that the great part of them come from the government in order to collect 'floating' money - riyals - that is in the hands of the people. This is one way to collect enough to pay their expenses."
Among the authorities there were "honest men dedicated to the revolution who are incompetent" and "corrupt parasites looking after themselves".
The Freedom Party has condemned the US for its policies towards Iran. "The Americans are hostile - and they have expedited and intensified their hostility towards our country", but he is curiously vague about the future of Iran, refusing to outline the programme his party would adopt if it is legalised and expressing only "optimism" "because I am a political activist". Perhaps it is the nebulous state of his party which produces such vagueness.
"They claim we are banned and we say we are legal. For two years we have been requesting the proper court to examine our case and have it rectified. The interior minister keeps saying the Freedom Party is not legal and we say to the minister that his statement is illegal because there is no law to limit our activities - and that therefore we are legal."