"Noting the fact that people's votes have no effect... and that there is no possibility for fair and free elections, there is no justification for people to participate in these elections," the Office to Consolidate Unity (OCU) said in a statement carried by the IRNA news agency on Wednesday.
The group, which had stayed out of the two-week-old crisis, called on the reformists to keep up their sit-in at the parliament building and to demand that the 20 February polls be postponed.
"Just as they have stood up honestly until now and have sworn to defend the rights of the people, they should also resist holding these elections," the OCU said.
"The biggest mistake and failure of the reformists will be to give in and accept to have these elections."
The OCU said the lawmakers should instead press for a referendum on the country's political future.
"The students ask for a referendum, which would provide a wise alternative to this political dead-end. The deputies should approve a proposal for a referendum," the statement said.
President Muhammad Khatami said on Wednesday it was too early to say if the crisis could be resolved.
Khatami's government is still in
talks with the Guardian Council
The embattled president said his government was locked in talks with the Guardian Council, a conservative political watchdog that prompted the stand-off.
"My government will organise free, fair and competitive elections. I will make all efforts for this to materialise, and I hope this will materialise," Khatami told reporters after a cabinet meeting.
"We are currently discussing with the Guardian Council and they know we have objections to the disqualifictions," he added.
"In the end it is not known if the outcome will be acceptable for us.
"I myself will not accept it even if one person is unfairly disqualified," he added.