Iran's hardline leadership today began a fresh crackdown against political opponents before elections to be held at the end of this week, announcing an investigation against a leading reformist for "treason".

As the last day of a muted campaign before Friday's largely discredited parliamentary poll neared an end, Gholam Hossein Mohseni Ejeie, the Iranian Intelligence Minister, denounced Noureddine Pir Mouazen, a reformist spokesman, as being guilty of an "appalling act" after he criticised the regime during an unauthorised interview with an American-backed television channel.

During the interview, broadcast by the Persian-language service of the Voice of America this week, Mr Mouazen became the second reformist leader in a matter of days to denounce the regime's decision to disqualify 1,700 candidates — including himself — from standing in the elections.

Dozens of Persian-language radio and television stations broadcast to Iran from the United States and Europe, but the authorities accuse them of containing anti-Islamic propaganda and have banned satellite dishes to prevent them from being seen. However, flouting of this rule is widespread.

Hours before Mr Mouazen's interview, Mohammed Khatami, the former reformist President of Iran, had claimed at a rally that the Guardians Council — a body of hardline clerics that vets candidates — was guilty of misusing Islam for barring the candidates. Many were banned for obscure reasons related to a lack of loyalty to Islam or the 1979 Islamic revolution.

Mr Ejeie also criticised Mr Khatami for holding a meeting with the German Ambassador, which a hardline newspaper claimed he had used to express concerns about the country's nuclear programme.

Iranian polls are widely discredited by the West because clerics regularly ban candidates from standing, and dissent against the regime is rare.

"This has definitely been treason and an appalling act," Mr Ejeie said, announcing an investigation into Mr Mouazen's interview. "The law bans people in such positions from interviews with foreign radios and television. The Intelligence Ministry will certainly probe this and will not ignore it."

Before Mr Mouazen gave his interview, the Guardians Council had already barred the 49-year-old from standing in the polls for the city of Ardebil in northwestern Iran.

As subtle dissent against President Mahmoud Ahmadinejad's regime appeared to be increasing, the conservative Government deplored Mr Khatami's meeting, Herbert Honsowitz, the German Ambassador without its permission.

"Contacting foreigners has certain codes and not everyone can talk over any issues to foreigners," Mr Eejie said.

"Such an act should be co-ordinated with the Foreign Ministry. It will harm the country and will be regarded as betrayal if issues against the system and domestic policies are discussed in these meetings which could be exploited by the enemies."

Iran’s hardline Kayhan newspaper had earlier accused Mr Khatami of discussing his concerns about the country's nuclear programme with the ambassador. A leading hardliner, Ruhollah Hosseinian, accused him of also meeting British diplomats.

"Reza Khatami has in past had such meetings with British diplomats to an extent that the British Ambassador expressed satisfaction with this meeting to their Foreign Office," he said. "I have enough evidence for these meetings."

Mr Khatami also attracted the attention of the regime last night for telling a large gathering of reformist supporters in southern Tehran late yesterday that "honest individuals" who were disqualified from running in the forthcoming elections "are portrayed as deviant and supporters of America. This is deplorable. Worse is that it is done in the name of Islam." The speech was posted on his website.

The latest developments came as Iranian political factions took part in the penultimate day of low-level campaigning before Friday's polls. The reformists will contest barely half of the 290 seats after 1,700 candidates were banned from standing.

Four main coalitions have emerged from the bewildering array of factions that make up Iran’s political scene. Conservatives have split into "Broad" and "Unified" factions, with the former seen as less enthusiastic about the populist policies of President Ahmadinejad.

Reformists are represented by a coalition inspired by former President Khatami and the National Confidence Party of the ambitious cleric Hojatoleslam Mehdi Karroubi — a more palatable option for conservatives.

The last week has seen election posters slapped on to billboards next to Tehran’s traffic-clogged roads and thousands of pamphlets of the various factions handed to passers-by.

Anxious for a show of national unity, the authorities want no repeat of the poor participation of the last elections, in which the turnout of 51.2 per cent was the worst in a legislative vote in the Islamic republic.

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