LONDON — Justice Secretary Kenneth Clarke was Wednesday battling to save his job after suggesting there was a distinction between "serious rape" and other forms of the crime.

The former shadow finance minister was taking part in a BBC radio phone-in when he replied to host Victoria Derbyshire's assertion that "rape is rape" by saying "no, it's not".

Clarke later Wednesday clarified he believed "all rape was a serious crime" but only said it was a "mistake" if his comments had "given any other impression" and refused to say sorry, angering women's rights groups.

The minister was invited on the show to explain government plans which could see certain rape sentences halved in the event of an early guilty plea in an attempt to increase the conviction rate for the crime.

Derbyshire presented Clarke with statistics showing that the average sentence for rape was five years.

The politician argued these figures included "date rape, 17-year-olds having intercourse with 15-year-olds.

"I don't think many judges give five years for a forcible rape, frankly. The tariff is longer than that," he continued.

"And a serious rape with violence and an unwilling woman, the tariff is much longer than that," he added.

"Rape is rape, with respect," Derbyshire replied, to which Clarke answered: "No, it's not.

"If there is an 18-year-old (who) has sex with a 15-year-old and she is perfectly willing, that is rape.

"Because she is under age she cannot consent. If anybody has sex with a 15-year-old, it's rape.

"So what you and I are talking about is we are talking about a man forcefully having sex with a woman when she does not want to," he concluded.

Clarke later Wednesday apologised to a rape victim whom broke down in tears during a conversation with the minister over the government's proposals.

Opposition Labour party leader Ed Miliband seized on Clarke's comments, saying he "cannot speak for the women of this country when he makes comments like that".

Vivienne Hayes, chief executive of the Women's Resource Centre, said the remarks "smack not only of ignorance but of outright misogyny".

"Attempting to apply a 'sliding scale' to so-called types of rape such as date rape further denigrates victims and lets off perpetrators too lightly," she added.