Standard & Poor's ratings agency upgraded its outlook on the U.K.'s triple-A credit rating from negative to stable on Friday.
The decision, announced after market close, will bolster U.K. Treasury chief George Osborne's argument that the country has turned a corner.
"We anticipate that the U.K.'s economic recovery will continue to broaden, benefiting the public finances," S&P said in a statement.
S&P is currently the only major ratings agency to retain a triple-A rating on British sovereign debt.
S&P also downgraded South Africa sovereign credit rating on Friday, from BBB to BBB-minus, but revised its outlook upwards from negative to stable.
The agency cited the prolonged strike in the country's platinum mining sector, as well as weak domestic and external demand, as reasons for the move, adding that financing relies on potentially volatile capital flows.