Moody's Investors Service on Friday cut the United Kingdom's credit rating to Aa1 from Aaa, citing weakness in the nation's medium-term growth outlook that it now expects to extend for a number of years.

The outlook on the credit is stable, the firm said in a statement.

Moody's said that despite considerable structural economic strengths, growth is expected to be sluggish due to a combination of weaker global economic activity and the drag on the UK economy "from the ongoing domestic public- and private-sector deleveraging process."

(Reporting by Daniel Bases; Editing by James Dalgleish)