ATHENS — The Greek government was plunged into chaos on Tuesday and faced an imminent collapse, as lawmakers rebelled against Prime Minister George Papandreou’s surprise call for a popular referendum on a new debt deal with Greece’s foreign lenders.

Such a collapse would not only render the referendum plan moot, it would likely scuttle — or at least delay — the debt deal that European leaders agreed on after marathon negotiations in Brussels last week, putting Greece on a fast track to default and raising the prospect of the country’s exit from the monetary union of countries sharing the euro currency.   Read more