New Senate will be unstable: Democrats

Outgoing Democrats Senator Natasha Stott Despoja says federal parliament's upper house after July 1 will be a very unstable place and there is a "hard, long road" of compromise ahead for the Rudd government.

The Greens, Family First's Steve Fielding and anti-pokies campaigner Nick Xenophon will hold the balance of power, ending the coalition's three-year control of the Senate.

Senator Stott Despoja said people had better get used to the situation.

"The government's going to have to bargain, and negotiate, and compromise, and do deals with the cross bench senators," she told reporters.

"Welcome to a very unstable place. Certainly after July 1, any one senator can kill a bill, or kill a government policy."

Senator Stott Despoja said balance-of-power situations in the past had worked well, especially when the Democrats held that balance.

But without the Democrats it was hard to predict what would happen.

"I suspect that some legislation will be held up.

"I'm sure some things will be blocked, but I can see a hard, long road of negotiation and compromise ahead for this government.

"My message today is ... who knows what the future holds?"

All four Democrats senators are leaving parliament at the end of this week after the party failed to win a seat at the November federal election.

But the Democrats are planning a comeback in a different guise, forming a new political entity with other minor parties.