The letter points out that since 2001, some 120 newspapers in Iran have been banned, more than 50 journalists have been detained and 11 remain in detention.
Earlier this month, the U.S.-based Human Rights Watch similarly criticized the EU's policy of dialogue, saying it had not had any tangible results.
The EU initiated its policy of dialogue at the end of 2002 with the hope of engaging Iran's rulers. Four rounds of talks have been held so far -- the latest held earlier this month in Tehran. No date has been set for a next round.
Human Rights Watch says that instead of easing repression, Iran has intensified its crackdown against critics and that numerous journalists and intellectuals have been prosecuted.
Jean-Paul Martoz, a Human Rights Watch spokesman in Brussels, told RFE/RL this month that the EU should take a tougher stance on Iran.
"We believe the EU should really establish clear benchmarks: ask for the release of political prisoners, ask for the reopening of reform-minded media, ask for an end of torture, clearly -- and should take that as benchmarks. [That means] that if the measures are not taken by the Iranian government, certainly the human rights dialogue should be stopped. If not, it would be just a sham, helping the conservatives in Iran to pretend that things are going well," Martoz said.
The EU -- while continuing to be critical of the human rights situation in Iran -- has defended its policy, saying it has led to minor yet positive steps. Michael Gahler is the European Parliament rapporteur for relations with Iran. He cites, as an example, a reduction in the number of Iranians held in prisons.
"There are some positive moves apparently in Iran,” he said. “They said that they earlier had 180,000 prisoners, [and now they have] only 130,000 -- so [this shows] they can reduce the figures of prisons. These are minor, positive steps."
The EU policy is credited with leading to a moratorium on stoning women accused of adultery and more frequent visits to Iran by UN rapporteurs on freedom of expression and arbitrary detention.
Gahler says dialogue is a way of supporting and encouraging those in Iranian society who are in favor of more democracy and more freedom. He recommends the EU broaden its contacts with Iranian civil society and pro-democracy groups.
He says the next EU presidency is planning to assess dialogue with Iran and its effects.
"The incoming Dutch presidency of the European Union said we will have an assessment of these two human rights dialogues. We have another one with China. We have to assess what effects it has had -- whether it is useful to continue. We cannot just continue saying we have a human rights dialogue forever and nothing changes. So we are waiting for this assessment. It is obvious [from] the Iranian side [that] their motivation primarily is to keep this dialogue and in the back [of their minds] they are [hoping for] a trade and cooperation agreement with the European Union. That is their prime interest. Therefore, they engage from their side, although at the moment in not a very forthcoming way. It remains to be seen how this will continue for the time being. I would say we should continue," Gahler said.
Progress on human rights and Iran's cooperation in three other sensitive issues -- nuclear proliferation, Middle East peace, and the fight against terrorism -- are viewed as preconditions that Iran must fulfill before the EU signs an agreement on enhanced trade and cooperation.