Greens Leader Richard Di Natale will look to expel members who undermined Alex Bhathal's bid for the federal Melbourne seat of Batman.

He said the party needed to find out who undermined the campaign and the Greens' chances to win the seat and would look to expel them from the party.

"They had a very deliberate agenda and decided to leak a number of things to the media in an effort to undermine us ... they set us an impossible task. I think that's grounds for expulsion," he told ABC TV on Sunday night.

"The people responsible for this have no place in our party. They should be expelled."

Former ACTU president Ged Kearney unexpectedly fought off the challenge of the Greens in Saturday's by-election with a swing towards Labor.

Greens Candidate for Batman Alex Bhathal is seen during a press conference with Greens Leader Dr Richard Di Natale on March 17. (AAP) (AAP)

The poll was brought on by former Labor MP David Feeney having to step-down over his citizenship status.

Mr Di Natale said it was a small group of people who had undermined the Greens' campaign and stirred up media attention to infighting among members.

"Unfortunately it was just a small amount of people with a destructive agenda to undermine a candidate and a campaign and we need to make sure that never happens again," he said.

But he would not state if he knew who was responsible.

"The people responsible for this have no place in our party. They should be expelled." (AAP) (AAP)

Mr Di Natale said the party would meet to discuss a culture change and put in processes to "make sure it never happens again".

"We are all here to support each other and that does not mean if you don't like a decision that has been made ... that you can take it upon yourself to leak and sabotage as a small group of people did," he said.

"All it takes is a couple of people."

Mr Di Natale also hosed down bullying allegations against Ms Bhathal, saying there was "no outstanding complaint" and it was unsubstantiated.