By Sudip Kar-Gupta
LONDON (Reuters) - The FTSE 100 fell towards five-month lows on Tuesday, with insurer Standard Life (LONDON:SL) and supermarket group Tesco (LONDON:TSCO) underperforming, as worries over Greece weighed on world markets.
The blue-chip FTSE 100 index was down by 0.6 percent at 6,578.81 points, near its lowest level since late January and extending losses after a 2 percent drop on Monday.
Standard Life was among the worst performers, falling 1.7 percent after analysts at RBC downgraded the stock to "underperform" from "sector perform".
Tesco also fell 2.3 percent and rival Sainsbury declined 1.8 percent after industry data showed that both companies had suffered a fall in sales.
Global markets have been rattled as a standoff between Greece and its lenders has intensified, with Greece just hours away from defaulting on a 1.6 billion euro ($1.8 billion) loan and at risk of sliding out of the euro zone.
Greek Prime Minister Alexis Tsipras has broken off negotiations with the European Commission, the IMF and the European Central Bank and announced a referendum on the country's bailout terms on July 5, giving voters just one week to debate the fundamental issues at stake.
"It's one of the biggest hurdles that the euro zone has faced. We could see the FTSE fall down to 6,400 points this week," said Logic Investments' Harry Shann.
The FTSE hit a record high of 7,122.74 points in late April but has since lost ground, as the concerns over Greece have knocked back European stock markets.
The FTSE is about 8 percent below the April record high and has erased nearly all the gains it had previously made in 2015.