Kimberely Kitching is being remembered as an "optimist, a realist and a believer" as the political world pauses to grieve the Labor figure.

Politicians from across the party divide have gathered at Melbourne's St Patrick's Cathedral to farewell the former senator, who died of a suspected heart attack on March 10.

Former Labor leader Bill Shorten, Ms Kitching's husband Andrew Landeryou and the Dalai Lama have led tributes to the 52-year-old.

"Politics can be, maybe it even has to be, fickle," Mr Landeryou said.