PM needs reminder of Senate roll: Brown

Malcolm Turnbull needs a constitutional history lesson to remind him of the role of the upper house, former three-term senator Bob Brown says.

Hours after the prime minister announced a double-dissolution election will be held on July 2 if the Senate doesn't pass anti-trade union legislation, the former Australian Greens leader said the upper house "is doing its job" by showing resistance to the bill.

"Sorry Malcolm, go back and see what the founding fathers said. The job of the upper house is to look at legislation and to improve it for the people and a draconian piece of legislation that seems to have been on the books for a long time seems to be the one that Malcolm Turnbull insists that the Senate pass."