The ratings agency said that while the British economy had dipped into a recession earlier this year, the second half was looking better due to progress in controlling the national debt.
"The stable outlook reflects our expectation that the U.K. government will implement the bulk of its fiscal consolidation program and that the economy should recover in the remainder of 2012 and strengthen thereafter," S-and-P said in a written statement.
Chancellor of the Exchequer George Osborne called S&P's move a vote of confidence in Britain's economic policy, the BBC said Saturday.
"The deficit has fallen by a quarter; inflation has fallen by half; employment is rising, with British businesses creating over 800,000 new jobs; and the economy is re-balancing, with Britain now exporting more to the rest of the world than Europe," Osborne said.
The Daily Telegraph said S&P issued its analysis just days after relatively disappointing growth figures that showed a slight economic contraction between April and June.