Bill Morris, the general secretary of the Transport and General Workers' Union, was accused of "sexist claptrap" as the union leadership battle became personal yesterday.
Jack Dromey, challenger in the forthcoming election, attacked Mr Morris after his wife, Harriet Harman, Labour's employment spokesman, was brought into the contest.
Mr Morris has questioned Mr Dromey's suitability because of his marriage. Sources have suggested that she would have divided loyalties over issues such as the minimum wage.
Mr Morris warned that Mr Dromey might "carve up" union policies "over the dinner table" to suit Labour and his close ally Labour leader Tony Blair.
The remark appeared to signify a new low in the bitter contest for the union's top post.
In response, Mr Dromey said yesterday on BBC Radio 4: "It is highly unfortunate that Bill attacked my wife, and it is sexist claptrap to suggest she can't look after her constituents and the interests of the Labour Party, and that I can't look after the interest of my members and rebuild theT&G." He said the couple both had a "very clear view" about the nature of the relationship, which was "built on independence and integrity''.