George Osborne's gloating over the economic recovery is unjustified and premature, Vince Cable has warned.
The business secretary's call for caution appears deliberately timed to clash with the chancellor's own triumphalist approach this week.
Osborne had claimed Britain is "turning a corner" in a speech at the start of the week. In Treasury questions yesterday he emerged from three years of defensiveness over the economy to an upbeat position he used to attack Labour's pessimism.
Cable's intervention will infuriate No 11. "Some of the reactions to the news over the last few weeks have somehow suggested we're out of this dark long tunnel," the business secretary told the Today programme.
"Until we get long-term sustained investment, a commitment to industry building up exports over a long period of time we will not have solved the problem."
In his speech later he is expected to say one of the dangers to the economy is "complacency, generated by a few quarters of good economic data".
Cable wants to portray the Liberal Democrats as taking a much more long-term approach to the economy than Labour or the Conservatives.
"The business investment figures over the last few months have been good. A few months is not years," he added this morning.
"I'm talking about different time periods. What we have to get embedded this time... it's got to be much more securely based on productive activities."
Cable's different approach to the issue, which he characterised as being based on the premise that "this is a marathon and not a sprint", is partly due to his role at the Department for Business, he claimed.
But his failure to reject the frustrations of outgoing Lib Dem MP Sarah Teather, who said she would leave parliament at the next general election in disgust at the compromises her party has made in government, is likely to leave party leader Nick Clegg as infuriated as the chancellor.
He praised Teather's resignation letter as having "very eloquently" outlined its arguments opposing the coalition's approach to immigration, which he made clear he disagreed with.
Home secretary Theresa May is currently developing plans to introduce immigration bonds, but Cable made clear he would fight them from within government.
"I think we're going to have to do this in a much more sensible way," he said.