Growth and borrowing forecasts contained in the government's 2013 Budget are unlikely to alter the "stable" outlook on Britain's Aa1 credit rating, Moody's said on Wednesday.

"Moody's is assessing the UK budget and expects that it will confirm the government's policy commitment to reverse the debt trajectory which, along with the country's underlying economic strength, underpins the stable outlook on the UK's Aa1 government bond rating," it said.

Moody's was the first of the major ratings agencies to knock Britain from its prized triple-A rating. It cut the rating from Aaa to Aa1 on February 22, citing the country's weak growth outlook.

Rival agencies S&P and Fitch still rate Britain AAA but with a negative outlook.

(Reporting by Christina Fincher)