Persson, who is due to join PR company JKL in August, was "watering down the integrity of politics," by Green Party spokesman Peter Eriksson, whose party cooperated with Persson's last government.
Eriksson characterize Persson's new job as "acting as a door opener for the highest bidder".
"He ought to be extra careful not to bring himself and the office of prime minister into disrepute," he said in a written statement.
Eriksson added that the Green Party had previously criticized former Social Democratic Industry Minister Björn Rosengren, when he shortly after his resignation in 2002 took a job as an advisor to the Stenbeck industrial conglomerate.
Persson is joining a sector that he himself has previously criticized and ridiculed, most recently in his last speech as party leader on March 17th.
"Lobbyists don't work for what is new. They work for what is old. The solutions of the future do not have lobbyists. It is the solutions of past that have lobbyists," he had then said.
He had also criticized the sector in a speech in 1997:
"What are these hired opinion-formers about - those who will one day sell their services to a company, the next day to a political party? What exactly is lobbying. What does it look like, how does it work? Are decision makers manipulated, do they have the wool pulled over their eyes? This is an important question in a democracy."
Mikael Giljam, professor of political science at Gothenburg University, criticized Persson for taking a job in PR so soon.
"It is most peculiar, I would say. He's doing a Rosengren or a [Carl] Bildt. The need for legislation and rules for recently departed ministers must now be an important question," he said.