"Stop this judicial process before it is too late," Arnon Bar-David, Israel's Histadrut union leader, said in a televised speech, addressing Netanyahu directly.
Protests have taken place across Israel for the last four months, sparked by anger at controversial judicial reforms pushed by Netanyahu's government, the most right-wing in Israel's history.
The planned overhaul would significantly weaken the country's judiciary and make it harder to remove Netanyahu, Israel's longest-serving prime minister, from power.
On Sunday, Netanyahu's office announced the dismissal of Defense Minister Yoav Gallant, who had opposed the motion, escalating protests.
"We must all stand up strongly against refusals," Netanyahu said on Twitter around the time of the announcement, without directly referencing Gallant.