The Tories will present their economic plans at their conference
Gordon Brown plans to leave any future Tory government a financial "scorched earth" by borrowing too much, shadow business secretary Alan Duncan says.
He told the BBC News Channel's Straight Talk that the prime minister wanted to "scupper" his party by leaving "a legacy afterwards which is difficult".
Mr Duncan also said "stability" had to be the economic priority.
The Tories are expected to outline more economic policies at their party conference in Birmingham from Sunday.
Mr Duncan's comments come as Mr Brown is the US for talks with President George W Bush on how to overcome the global economic downturn.
Asked what an incoming Conservative government would do first, he said: "We'll have to see the state of accounts when we get there but, let's face it, it's going to be very difficult.
"We handed over to the Labour Government in '97 the best ever economy and at the end of this period of a decade we should have lower taxes, a massive pensions pot, higher savings and not so much borrowing as a surplus."
He added: "The priority is going to have to be stability. Now there are so many variables in any kind of Exchequer decision.
"It's not just tax and spend; it's what happens should you cut taxes with the inflow.
"Sometimes you can cut taxes and revenues go up - that's quite possible with things like inward investment - but we are not going to write our first Budget now, we don't know.
"[Shadow chancellor] George Osborne doesn't know, but what we are saying is stability and we are not going to be reckless or hard with people who expect help."
Mr Duncan went on to say that "I'm not going to fall into Gordon Brown's trap which is actually to leave scorched earth.
"I think he is deliberately now borrowing too much in the hope that he leaves a legacy afterwards which is difficult for us...
"I think every single day of his political life he's tried to scupper us but he's now scuppering himself."
In a speech to the UN General Assembly on Friday, Mr Brown called for changes to the way markets and the financial sector are regulated.
He said: "This cannot just be national anymore. We must have global supervision...
"The age of irresponsibility must be ended. We must now become that new global order founded on transparency, not opacity."
Straight Talk is on Saturday at 0130 BST, 0430 BST, 2230 BST, and on Sunday at 0130 BST and 2230 BST.