Vince Cable has dismissed criticism over text messages he exchanged with opposition leader Ed Miliband.
Former Liberal Democrat leader Sir Menzies Campbell warned the Business Secretary that such communication could undermine the coalition by aggravating already disgruntled Tory backbenchers.
But Mr Cable told ITV1's Daybreak: "In politics you have to have a reasonably adult way of dealing with people. I very, very occasionally talk to Ed Miliband and sometimes his people, and indeed people across the spectrum."
When asked if he was annoyed that the Labour leader had made their communication public, he replied: "It doesn't matter. There's nothing to be embarrassed about for him or for me. I talk to people across the political spectrum.
"I think that is what politics involves, being grown up, not being tribal. I don't feel remotely embarrassed about it."
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?"
Mr Cable's aides dismissed the criticism of the text exchanges between the Business Secretary and the Labour leader.
"Vince is not looking for a new partner. He is clearly happy in his job and is delighted with his new team and the big hitters in the department. He is committed to the Coalition Agreement.
"Vince has always talked to politicians of all colours. He has had occasional but infrequent texts with Ed Miliband about substantive issues of policy such as House of Lords reforms."