Ratings agency Fitch has confirmed speculation and cut ratings across the UK banking sector, downgrading part-nationalised lenders Lloyds and Royal Bank of Scotland (RBS) due to uncertainties about the level of government support that they may receive.Ratings for Lloyds and RBS - which were already cut by Moody's last week - have been slashed from AA-to A, causing both stocks to sink on Thursday afternoon. RBS is 83%-owned by the state, while taxpayers have a 41% stake in Lloyds.Fitch now has them on a stable outlook.Barclays, while holding on to its AA- rating, was also under the cosh after the agency placed the firm on negative watch. Barclays has never taken direct state support.Fitch claims that these banks are now less likely to receive government support in the future. There is now more political will to reduce support at the country's banks after last month's proposals by the Independent Commission on Banking (ICB) to increase minimum capital requirements and to separate retail arms from investment-banking activities, the agency said.By 15:49, RBS was 4.2% lower while Lloyds and Barclays were both down 5.1%.MG/BC