Senator Kitching's funeral will be held on Monday after she died suddenly last week from a suspected heart attack at the age of 52.

Labor frontbencher Bill Shorten has suggested the senator was stressed about her pre-selection for her Victorian Senate seat.

But Senator Farrell, who counted himself as a close friend of the late senator, said there was no reason for her to have felt that way.

"I don't think there was any prospect at all of her losing her pre-selection, to be perfectly honest," Senator Farrell told Sky News' Sunday Agenda program.

"She was supposed to call me the day she died to talk about that and I was certainly of the view that she would be re-endorsed, there was no other candidate I don't believe to replace her."

Senator Kitching's sudden death has also raised claims she was bullied by the Labor hierarchy in the Senate.

But Penny Wong, Labor's Senate leader, has denied such allegations.

"There are views that have been shared and claims that have been made which we don't - which are not true," Senator Wong reiterated on the Nine Network.

But Scott Morrison said they are serious allegations that Opposition Leader Anthony Albanese has to deal with.

"He needs to be able to face up on this and say what he is going to do about this. So far, he seems to just dismiss the issue completely," the Liberal prime minister told reporters in Sydney.

Australian Associated Press