In recent months, former reporters and anchors say, the network has been used to serve the political agenda of its owner and founder, Sheik Hamad bin Khalifa al-Thani, the emir of Qatar, Der Spiegel reported Friday.
The network went on the air in 1996 with a stated goal of serving as an objective source of information in a world of censorship.
"Before the beginning of the Arab Spring, we were a voice for change, a platform for critics and political activists throughout the region," said Aktham Suliman, who worked at al-Jazeera's office in Berlin. "Now, al-Jazeera has become a propaganda broadcaster."
Another former correspondent said decisions at the network were no longer based "on journalistic priorities, but rather on the interests of the Foreign Ministry of Qatar."
The network ignored mass protests against the Bahraini government, an ally of the emir, the journalists said. In Syria, where Qatar supports the opposition to President Bashar Assad, al-Jazeera favors the rebels.
And then there is the attitude al-Jazeera appears to have about some of its journalists. A sniper in Syria recently killed a person who worked part-time for the network. Although it is standard practice for networks to provide bulletproof vests to its reporters working in combat situations, al-Jazeera had declined to do so after saying it would.
"If a differentiation is no longer made between activists and journalists, then that poses a danger to everyone," Suliman said.
The resignations by al-Jazeera journalists in cities such as Paris, London, Moscow, Beirut and Cairo came as the network paid $500 million for Current TV in a gamble to enter the U.S. market.