Former Labor prime minister Julia Gillard offered to resign in favour of Greg Combet at the height of Labor's leadership instability ahead of the 2013 election.
Mr Combet makes the explosive claim in a new book about his time in politics.
The former climate change and industry minister has revealed he spoke privately to Ms Gillard about the difficulties she faced in a closed door meeting.
"I thought there needed to be a caucus ballot for the leadership once and for all, we couldn't have had two leaders going to the election fighting Tony Abbott which was the situation we were in," Mr Combet has told the ABC's 7.30 program.
"Julia surprised me at that discussion by suggesting she would stand down in favour of me if I stood".
Mr Combet added that he didn't know if he would have won in a ballot against former prime minister Kevin Rudd.
Mr Combet says he was also offended by Mr Rudd's suggestion, in 2007, that he needed to be "de-unionised" after being elected to parliament "a bit offensive".
more to come
