More than 100 Iranian MPs have resigned in protest at the barring of thousands of candidates in parliamentary elections later this month.
The lawmakers' move escalates the crisis
In a speech on behalf of fellow lawmakers - carried live on state radio - Mohsen Mirdamadi spoke of an "ugly body of dictatorship" in Iran.
President Mohammad Khatami has demanded that all those banned by the hardline Guardian Council, be reinstated.
Mr Khatami made a public appearance on Sunday - a day after falling ill.
On Friday, the hardline-dominated Council - a 12-member unelected body - reinstated a third of the 3,600 candidates it disqualified from the election due on 20 February.
But it falls far short of the full reinstatement demanded by protesting reformist MPs, 80 of whom are themselves on the blacklist.
Interior Minister Abdolvahed Moussavi Lari, who is in charge of organising the poll, has warned that it will be "out of the question" to hold elections.
"The possibility of organising a free and competitive election does not exist," he said.
Iran's conservatives lost control of the parliament to the reformists in elections in the year 2000.
Parliament Speaker Mehdi Karroubi told the house he had received 109 resignation letters from lawmakers.
"We are all very sorry and regretful about this issue," Mr Karroubi said, blaming the conservatives: "One [political] faction lacks the support of the people. They want to gain it by force through the Guardian Council."
IRAN'S REINS OF POWER
Supreme leader Ayatollah Ali Khamenei: Appointed for life, overrides all other authorities (pictured above)
Guardians Council: Half chosen by Khamenei, responsible for vetting election candidates and laws
President Mohammad Khatami: Elected for four years, power can be circumscribed by clerics
Parliament: 290 members introduce and pass laws, subject to approval
Fellow MP Rajab Ali Mazrouie said that, with the ban, the result of the poll would be a foregone conclusion.
"An election whose result is clear beforehand is a treason to the rights and ideals of the nation," Mr Mazrouie told the 290-member body.
It is not clear whether the resignations would take effect immediately - or whether they will have to be approved by some other body.
And Mr Karroubi has appealed to Iran's Supreme Leader, Ayatollah Ali Khamenei, to intervene to resolve the crisis.
So far, there has been little public reaction to the political crisis, which began with the mass disqualifications on 11 January.
There is disillusionment among the people, says the BBC's Miranda Eeles in Tehran, because they have seen the efforts of the reformists they elected last time thwarted by the unelected hardliners.
The MPs found they had to take action, our correspondent says, after an emergency cabinet meeting scheduled for Saturday was cancelled because President Khatami fell ill.
Sources close to the 60-year-old president blamed stress and pressure on his nerves for the illness.
But a day later, he was shown on state television inaugurating Imam Khomeini International Airport in Tehran.
Khatami was said to have fallen ill because of stress
Before he was taken ill, President Khatami reportedly said his government "will only organise free and competitive elections".
Mr Lari had earlier requested the postponement of the poll - scheduled for 20 February - but the Guardian Council said it saw no reason to do so.
The political row worsened as Iran prepared to commemorate the 1979 Islamic revolution that toppled the pro-US leadership and brought to power anti-American hardline clerics.