Shadow chancellor Ed Balls has challenged George Osborne to a head-to-head TV debate ahead of the general election.
Mr Balls got the chancellor to shake hands on it on the Andrew Marr programme after making the surprise offer.
Mr Osborne said he would be "happy" to meet Mr Balls in a debate.
But he added that the Lib Dem chief secretary to the Treasury Danny Alexander would want to be part of it.
Mr Balls caught the chancellor off guard with the offer of a debate at the end of the programme, when they were sitting together on the studio's sofa.
'Up for it'
Asked if he was interested in a debate, Mr Balls replied: "Of course, and I would like to go further - George and I don't need the broadcasters to sort these things out.
"George is not a coward. David Cameron doesn't want a head-to-head with Ed Miliband but I'm very happy - I will have a head-to-head debate, just the two of us, the potential chancellors during the election campaign."
Addressing Mr Osborne, he said: "You can say now - are you up for it?"
The chancellor replied: "As I say, happy to have this chancellors' debate, just as we did in the last election."
"Come on George, let's go for it," said Mr Balls.
"Well I'm happy to meet you in a debate," replied Mr Osborne.
"We should shake on it and go for it," said the shadow chancellor, offering his hand.
Appearing hesitant, Mr Osborne shook on it but added: "Ed I'm not going to... we're going to see who else wants to be part of that. I've got a very effective chief secretary, who I think would also want to be part of that debate."
Mr Balls added: "If only David Cameron was up for a one-to-one debate like George, it would be all right. For some reason, David Cameron is running scared."
Mr Osborne said: "I think we should include Danny Alexander."
Mr Balls countered: "No, one-to-one. We just shook on it."
Speaking later on BBC Radio 5 Live's Pienaar's Politics, Mr Balls said he initially thought Mr Osborne had agreed to a debate, but "by the end of the handshake there was constructive ambiguity I think".
He later issued a statement accusing the chancellor of trying to "wriggle out" of a head-to-head debate with him.
"It's good that George Osborne shook hands on a head-to-head TV debate with me during the election campaign," he said.
"But he's already trying to wriggle out of that by insisting on bringing his deputy along.
"If George Osborne wants a debate with all the main parties, as well as a head-to-head debate, that's fine by me.
"But we need a head-to-head debate because there's a big choice between an extreme Tory plan which will put our NHS at risk and Labour's better plan which will put working families first and save the NHS.
"And David Cameron must now stop running scared of his record and finally agree to a head-to-head TV debate with Ed Miliband."