Vince Cable has dismissed criticism from former Liberal Democrat leader Sir Menzies Campbell over text messages he exchanged with opposition leader Ed Miliband.
Sir Menzies Campbell warned the Business Secretary that such communication could undermine the coalition by aggravating already disgruntled Conservative backbenchers.
But Mr Cable told Sky News: "I don't know what the problem is.
"I do very, very occasionally talk to the leader of the Labour Party and other people across the political spectrum about matters of national interest. Surely that's grown up?
"You should be able to talk to people outside of your own party, but I am very firmly committed to working in the coalition Government. I have an important job to do and I am getting on with it.
"We will go into the next election with our own distinct philosophy and policies.
"But in the meantime - and we have got quite a long time before the next general election, well over two years - we are committed to working under the coalition agreement that we've negotiated, and I have an important job within that agreement and I am committed to that work.
"At the same time I have a very relaxed approach to talking to other people, and I simply see that as basically, fairly adult, and I really don't see what the problem is."
In an interview with The House magazine, Sir Menzies said: "The success of this coalition depends upon everyone who participates in it being a full subscriber, and I don't think, we were using the expression pick and mix a little while ago, I don't think it helps a partnership to suggest that you may already be looking for another partner.
"If you were a Tory backbencher hearing of these things, especially one who's disaffected, who wishes there was an unrestricted Tory government, what would you make of it?
"Would you be encouraged to be yet more loyal to the front bench or would you say well, that's a kind of, maybe, not a green light but an amber light. Proceed with caution. An amber light to people like myself to say well, if so and so looks as if he's talking to the other lot why are we are bothering with this lot?"
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