Parliament has had an uneasy relationship with the country's reformist media since hardliners won a majority of seats in the assembly in February 2004 elections.
"You are a bunch of liars who don't believe in anything and lie for a loaf of bread," hardline member of Parliament Mehdi Kouchakzadeh was quoted by the official IRNA news agency as saying to a reporter in parliament this week.
About 60 journalists, who held banners reading "Stop the crackdown on the press" and "Insulting reporters is insulting freedom", took part in Sunday's protest in the capital, Tehran.
"We want that lawmaker (Kouchakzadeh) punished," said Iran's Press Association spokesman Mashallah Shamsolvaezin, who led the protest. "The parliament speaker must apologise to journalists from the parliament's podium," he said.
Shamsolvaezin blamed outgoing reformist President Mohammad Khatami for what he called a new wave of attacks against media.
"The parliament speaker must apologise to journalists from the parliament's podium"
Press Association spokesman
"The closer he gets to the end of his term, the president is becoming more and more indifferent about press freedom. I hold him responsible, too," he said.
Shamsolvaezin said protests would continue until lawmakers apologised.
Almost 100 publications have been shut down by the judiciary since 1999, and many journalists and writers have been jailed for crimes such as "spreading lies" and "acting against state security".