European stocks slid the most in a month amid growing concern that Greece may leave the euro as the region’s leaders prepared to meet in Brussels.

Greece’s former Prime Minister Lucas Papademos said that while it is unlikely the nation will leave the euro, it’s still a risk, the Wall Street Journal reported yesterday after the close of European trading.

European leaders are meeting in Brussels today to discuss the region’s debt crisis that has wiped about $4 trillion from equity markets worldwide this month. German Chancellor Angela Merkel has been unable to stifle calls for measures she opposes, including euro bonds, the use of European money to recapitalize banks, a bigger rescue fund and extra time for debt-swamped countries to cut spending.

National benchmark indexes fell in all the western European markets today, except for Iceland. The U.K.’s FTSE 100 lost 2.5 percent and Germany’s DAX slid 2.3 percent. France’s CAC 40 sank 2.6 percent.

LSE plunged 7.3 percent to 947 pence, the biggest drop since November 2009. UniCredit and Intesa Sanpaolo, Italy’s biggest banks, sold about 31 million shares at 960 pence apiece, according to statements from the lenders.

FirstGroup Plc rallied 7.4 percent to 220.1 pence. Britain’s largest train operator boosted full-year earnings 90 percent and said it would accelerate an asset-disposal program in its bus division.