"We are speaking for the people, it is not in favour of the country. Thirty crore people will be unemployed," he said.
He also questioned how the US gained from organised retail.
"If this was good and beneficial, why is America in trouble? Why are people unemployed there," he asked.
Recalling Mahatma Gandhi's policy of "swadeshi" (indigenous), he said: "When Gandhiji burnt foreign clothes, they were of good quality. A Britisher asked why was he opposing it. He said, 'we are doing it to save our handlooms'. Please listen to Gandhi, he was in favour of swadeshi."
Mulayam Singh added: "You will not benefit from this (FDI in retail) even in elections. We may not come to power at the centre but we will support you, and take support from you as well."
The SP is extending outside support to the UPA government.