Vince Cable has dismissed a warning by senior Lib Dem colleague Sir Menzies Campbell about his text exchanges with Labour leader Ed Miliband.
Mr Miliband recently revealed he swaps texts with Mr Cable, most recently on Lords reform.
Sir Menzies said this gave the wrong impression about his party's commitment to the coalition with the Tories.
But Mr Cable said he did not see "what the problem is" and he remained "committed to the coalition".
Speaking on Sky News, the Lib Dem business secretary said he did "occasionally talk to members of the Labour party on important matters of national interest".
But he said that he was "committed to the coalition", and had a very important job within that coalition.
He said that the coalition partners would go into the next election with distinct philosophies and politics.
Amid speculation about Nick Clegg's long-term future, shadow chancellor Ed Balls recently indicated that he and Mr Miliband could not see themselves working with the Lib Dems while Mr Clegg was leader.
But Mr Balls suggested he could work with Mr Cable, who was acting Lib Dem leader before Mr Clegg's election to the post and worked behind the scenes for Labour ministers in the 1970s.
Earlier on ITV's Daybreak, Mr Cable was asked if he was annoyed the Labour leader had revealed the contact between the two men.
He said: "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."
Sir Menzies said such disclosures gave the wrong impression about his party's commitment to the coalition with their Conservative partners.
"The success of this coalition depends upon everyone who participates in it being a full subscriber," he told the House magazine.
"I don't think it helps a partnership to suggest that you may already be looking for another partner."
Any talk of fraternization with Labour at the moment could encourage restive Conservative MPs to be less loyal to the government, he suggested.
On Thursday, Deputy Prime Minister Nick Clegg said he would consider entering into coalition talks with Labour after the next general election.
The Liberal Democrat leader told an audience in Cambridge if a coalition between the Lib Dems and Labour was viable "we would enter in to talks in good faith".