LONDON ¨C Britain suffered further blows to its economic standing on Monday as two top ratings agencies downgraded its sovereign credit score, judging last week¡¯s vote to leave the European Union will hurt its economy.

Standard & Poor¡¯s stripped Britain of its last remaining top-notch credit rating, dropping it by two grades from ¡°AAA¡± to ¡°AA¡± and warning more downgrades could follow.

Fitch Ratings also downgraded its ranking for Britain¡¯s creditworthiness by one notch, and similarly said more cuts could follow.

The ratings agencies effectively added a rubber stamp to the market¡¯s view of the Brexit vote, as sterling tanked to a 31-year low against the dollar on Monday and stock markets fell for a second trading day since the referendum last Thursday.

It was the first time S&P had chopped an AAA-rated sovereign credit rating by two notches in one move.

¡°In our opinion, this (referendum) outcome is a seminal event, and will lead to a less predictable, stable and effective policy framework in the U.K.,¡± S&P said in a statement.

Chancellor of the Exchequer (finance minister) George Osborne said Monday the British economy is strong enough to cope with the volatility caused by Thursday¡¯s referendum.

But the vote has plunged the country into a political crisis, with the ruling Conservative Party looking for a new leader after Prime Minister David Cameron said he will stay on until October, delaying the launch of negotiations with the EU and leaving the country¡¯s economic prospects under a cloud of uncertainty.

The added prospect of a new independence referendum in Scotland, which voted strongly to stay in the EU, threatens the constitutional and economic integrity of the United Kingdom, S&P warned.

Fitch more than halved its growth forecast for Britain¡¯s economy in 2017 and 2018 to just 0.9 percent for both years, from 2 percent previously.

Long-dated U.S. Treasury yields fell to session lows after S&P¡¯s decision. British 10-year government borrowing costs had already fallen below 1 percent for the first time during European trading hours.

S&P warned financial firms, especially foreign ones, might look to other destinations for investment after Britain leaves the EU.

The remaining major ratings agency, Moody¡¯s, which took away Britain¡¯s AAA-rating in 2013 because of the country¡¯s high levels of debt and slow growth, said Friday it could cut the rating further.

Moody¡¯s will downgrade the credit rating outlook for major British banks to ¡°negative¡± on Tuesday because of the fallout from the vote to leave the EU, Sky News reported, citing sources.

Protecting Britain¡¯s credit rating was a top priority of Osborne when he came to power in 2010.