Nick Clegg has said shadow chancellor Ed Balls is the only politician with whom he has a personal feud.
The deputy prime minister said he made it a rule to keep arguments focused on policy, but he "made an exception" for the combative Labour MP.
The comments came in a special Christmas edition of Clegg's LBC radio show at Great Ormond Street hospital in London.
Answering questions from an audience of young people, the Liberal Democrat leader revealed that two of his sons had needed hospital treatment in the past.
He also said his mother had inspired his political career, and disclosed that he and his siblings secretly insult people in Dutch.
Asked what techniques he used to win people over in discussions, Clegg said: "I always try to keep a good sense of humour, and if I have an argument with someone to keep the argument about what the argument is about and not allow it too often to become sort of personal.
"I make one exception, for a man named Ed Balls. But other than that I try not to make it about insults and stuff."
Clegg said he had been treated in an NHS hospital before, but not for anything major.
"Two of my children have been in hospital in the past, one of them quite seriously," he added.
"Like all families we have been in and out and depend massively on the NHS."
Clegg was challenged to say what he found most useful about being able to speak five languages.
"Probably the most useful is that my brothers and sisters and I can say slightly rude things about people in Dutch confident in the knowledge unless they're Dutch speakers they don't know what we're saying about them," he said.
"There has actually been a case where said something slightly rude about someone in a lift... in Dutch and the person just turned around in Dutch and said 'we understand every word you've said'."
Clegg reiterated his opposition to the 11% pay rise for MPs announced by the Independent Parliamentary Standards Authority (Ipsa) earlier this month.
"I hope it won't happen, and it is wrong, and it shouldn't happen. I very much hope it won't," he said.
He stressed that the watchdog was "completely independent" of government, but urged it to think again before finalising the proposals after the general election in 2015.