The rating agency late Friday affirmed its "AAA" long-term rating for the country, the same day as the Olympics got under way in London.
The U.K. economy slipped into a recession earlier this year, putting pressure on Prime Minister David Cameron and his government's efforts to cut spending and balance budgets. S&P said it expects the economy to recover in the second half of this year and that the government will keep budgets tight.
Last week, the International Monetary Fund said Cameron's government may have to ease up on budget cutting if the economy continues to struggle.
S&P said it expects the Bank of England to keep interest rates low to help the economy.