Justice Secretary Ken Clarke has admitted he got "bogged down" in an argument about different types of rape.
He told BBC One's Question Time his comments about the differences between "serious, proper rapes" and others had "obviously upset a lot of people".
But Mr Clarke insisted plans to halve sentences for criminals who admit guilt at their first chance to enter a plea after being charged were still being considered.
Mr Clarke has said he will not resign.
Labour leader Ed Miliband called on him to step down following his comments on BBC Radio 5 live on Wednesday.
Mr Clarke told Question Time, filmed this week at Wormwood Scrubs prison in west London: "I obviously upset a lot of people by what I said and I'm sorry if I did, by the way I put it.
"All rape is serious. It's one of the gravest crimes. My choice of words was wrong. It's because I got bogged down in a silly exchange."
'Very badly phrased'
He added: "As a politician I made a mistake by allowing myself to get drawn into a great long argument about exactly what the gradations of rape were.
"I phased it very, very badly because I upset a lot of people who want to give more priority to rape."
The row began on Wednesday morning when the justice secretary gave an interview to BBC Radio 5 live about proposals to halve jail terms for people who plead guilty early, including rapists.
Currently, offenders who plead guilty at the earliest opportunity are entitled to a reduction in their sentence up to a maximum of 33%. The government is consulting on extending that to 50%.
During the 5 live interview, Mr Clarke disputed reports that the current average sentence for rape was five years and insisted that "serious rape" attracted a much longer term.
Mr Clarke told Question Time: "I was trying to point out that rapists get much longer than she was saying.
"The average is eight years. My reform proposals don't affect the sentencing framework for rape or any other crime."
The justice secretary also said the whole row had been a "media brouhaha".
Mr Clarke said his sentencing proposals, which are understood to have been delayed until next month, would apply to "every crime".
Asked what he meant by an early guilty plea, Mr Clarke said he was referring to offenders who admitted their guilt at the first possible opportunity to enter a plea after being charged.
BBC home affairs correspondent Danny Shaw said the proposal to change sentencing guidelines was crucial to the Ministry of Justice's cost-cutting plans.
The department estimates it would save 3,400 prison places - and £130m - per year by 2015. That saving represents 62% of the £210m a year it has promised to cut.
Labour leader Ed Miliband later told MPs it suggested there were "other categories of rape" and called on him to resign.
Jack Straw, Labour's former home secretary, also appearing on Question Time, said: "If this had happened to me, the fury, not least from the Conservative benches, would have been such that I would have been moved on to a different job.
"If you get into that situation you need to deal with that very quickly. I would have apologised. If you're in politics at the high level, there are going to be days when the words don't come out properly."
Asked if Mr Miliband had been right to call for Mr Clarke to be sacked, Mr Straw replied: "My leader is always right."
After Mr Clarke's radio comments, David Cameron told MPs rape was "one of the most serious crimes that there is and it should be met with proper punishment" and the "real disgrace" was that only 6% of reported rape cases ended in a conviction.
The prime minister's spokesman said it was "clearly regrettable" if anybody had been offended by Mr Clarke's comments.
He added that no final decision had yet been taken on whether to increase the maximum sentence discount for a guilty plea, saying: "We are not setting out the policy imminently and clearly we continue to listen to people's views."