Dozens of labor and independent trade union activists are in prison for speaking out in defense of workers.

Human Rights Watch called for the government to end the crackdown and free labor rights advocates in anticipation of International Workers’ Day on May 1, as part of a joint campaign by Iranian and international rights groups to highlight the plight of workers.

Labor rights groups say that the rights of Iranian workers have come under increasing attack during the presidency of Mahmoud Ahmadinejad. Security forces have harassed and arbitrarily arrested an increasing number of striking workers, who are then subjected to politically motivated prosecutions and unfair trials.

“Iranian workers are on the front lines of the struggle to demand such basic rights as freedom of assembly and association, “said Sarah Leah Whitson, Middle East director at Human Rights Watch. “They are often the first victims of government crackdowns that aim to silence criticism.”

The Iranian government’s stranglehold on unionization and crackdown on labor rights activists have left workers without a voice to influence government policy and working conditions, even as the country’s worsening economic situation is pushing many into poverty, Human Rights Watch said.

Independent trade unions are banned in Iran. More than a dozen labor activists are in prison for exercising their right to freedom of assembly and association. Many others have been released on bail, with cases pending against them in revolutionary courts.

Earlier in 2013, Iran’s Supreme Work Council, a government body charged with promulgating labor regulations, set a 25 percent minimum wage increase (487,000 toman per month, about US$ 140) for the coming year. A group representing Tehran workers at the Islamic Labor Council, a state-sanctioned body that ostensibly acts to protect the rights of workers in lieu of independent trade unions, has officially submitted a complaint to the body demanding a larger increase.

Article 41 of Iran’s labor law requires authorities to take the rate of inflation into account when establishing the minimum wage. The official inflation rate is close to 32 percent, but many economists say the real rate may be above 50 percent.

Iran’s labor law does not recognize the right to create labor unions independent of government-sanctioned groups such as the Islamic Labor Council. Nonetheless, workers have formed large, independent unions, including the Syndicate of Workers of Tehran and Suburbs Bus Company, Haft Tappeh Sugar Cane Workers’ Syndicate, and the Iran Free Workers’ Union.

Since 2005, authorities have repeatedly harassed, summoned, arrested, convicted, and sentenced workers affiliated with these and other independent trade unions.

Most of these arrests have taken place during International Workers’ Day celebrations or strikes the unions have called.

About 80 percent of workers are working under temporary, short-term or at-will employment arrangements, which severely restrict their benefits and provide little protection from summary firings by business owners, labor activists say.

The situation is particularly dire for the most vulnerable workers: women, children and Afghan migrants.

“Regardless of sanctions or other causes of economic hardship in Iran, workers should have the right to organize, strike, and hold sit-ins, and speak out against government policies they consider harmful,” Whitson said. “The worsening crackdown on workers who try to exercise their rights is a flagrant violation of the Iranian government’s obligations to its people.”