The chancellor was set to be moved to another department in a cabinet reshuffle last summer, to make way for schools secretary and Brown ally Ed Balls.
He told the Prime Minister that he would return to the backbenches rather than take a different cabinet job, but insists there was no ill feeling.
“I’ve always said to Gordon that it’s his government, but I enjoy doing this job and I wouldn’t want to do any other,” he said.
Meanwhile, Brown has pledged to keep Darling in his job should Labour win the general election.
The Tories are convinced that Balls will become chancellor if Brown clings to power.