All major global indices posted substantial losses in early trading over growing concerns the debt crisis in the eurozone may spread to Italy and Spain.
The FTSE has plunged into negative territory after disappointing US jobs data reignited fears over the economic recovery.
London's leading index has edged through the 6,000 point barrier for the first time in over a month, despite Standard & Poor's warning on Greece.
Nervous markets were further soothed yesterday as Greek MPs passed a law to implement strict austerity measures in a second round of voting.
Global markets surged this morning following yesterday's green light for Greece's five-year austerity plan.
London's leading share index has broken through the 5,800 barrier, boosted by strong showings overnight in the US and Asia, and ahead of a crucial vote in Greece.
The FTSE 100 is edging towards 5,800 early on amid a wave of optimism Greece will pass its five-year austerity plan.
US markets got off to a mixed start Monday as European nations continued to debate the future of Greece.
European markets rallied this morning on news the European Union will support troubled Greece if it introduces additional spending cuts and a privatisation programme.
US markets reversed falls on Monday after a period of consecutive weak sessions fuelled by concerns over the end of quantitative easing.