Banks are among the worst performers on a tough day for the markets, most notably part-nationalised Royal Bank of Scotland. The taxpayer-owned bank has agreed to pay the US government $500m to settle charges it conspired to violate the US Bank Secrecy Act. The Department of Justice said ABN Amro, the lender RBS bought in 2007, had helped banks and customers from blacklisted countries, such as Cuba, Iran, Libya, and Sudan, to carry out transactions. Barclays and Lloyds are also suffering as nerves set in across the banking sector over the plan to bail out the euro agreed by European governments yesterday.Mining stocks are also lower as metals slip back amid concerns over the effect of any failure of the deal on the global economy.Sector heavyweights such as Xstrata, Kazakhmys, Vedanta and Rio Tinto are nursing losses, having jumped yesterday.Top performing sectors so far todayFixed Line Telecommunications 1,757.41 +1.11%Bottom performing sectors so far todayMining 20,976.12 -3.88%Industrial Metals & Mining 5,546.74 -3.44%Real Estate Investment & Services 1,482.74 -3.43%Banks 4,848.52 -2.84%Financial Services 4,836.19 -2.17%