But Mr Dreyfus - a senior member of the Opposition Leader's frontbench team - has not followed through on that threat and Ms Kitching was parachuted into the plum Victorian Senate seat vacated by Stephen Conroy, another ally of Mr Shorten in the Victorian right faction.
In question time on Wednesday, manager of government business Christopher Pyne stepped up his attack on Mr Shorten and Ms Kitching over the appointment, while challenging Mr Dreyfus to deny his threat to resign.
"The Leader of the Opposition deliberately parachuted into the Senate Kimberley Kitching to become Senator Kitching, who is alleged to have fraudulently filled out the safety tests for six union leaders in the Health Services Union," he said, labelling the new senator a "Captain's Pick".
The decision to install Ms Kitching had been made despite the "complaints, the outrage of many members of his frontbench, particularly the member for Isaacs [Mr Dreyfus], who threatened to resign if Kimberley Kitching was appointed to the Senate - and if it is not true, he is welcome to say that he was misrepresented and explain the facts".
When question time finishes, MPs are given the opportunity to make a public statement when they believe they have been misrepresented by an opposition MP or in the media.
Since his election to Parliament, Mr Dreyfus has shown a notable fondness for making such statements. But he made no such statement in Parliament on Wednesday.
In response to questions from Fairfax Media, Mr Dreyfus did not deny he had threatened to resign, nor did he elaborate on why he had not followed through.
Instead, he said: "Christopher Pyne is obsessed with the Labor Party. He should quit gossiping about me and take his job as a minister seriously. Senator Kitching will make a strong contribution to the Parliament as a Senator and I'm looking forward to working with her."
Ms Kitching, who is politically close to Mr Shorten, was a controversial appointment and the move was privately opposed by many in the ALP, though she was eventually selected unopposed by Victorian Labor's 100 person Public Office Selection committee. Labor frontbencher Anthony Albanese refused to endorse her for the seat.
At the same time, the federal government has used Ms Kitching's elevation - and the fact that she was referred for "further investigation" by the Heydon royal commission into trade unions - to attack the Opposition Leader.