Britain's FTSE 100 <.FTSE> fell to one-month lows Tuesday as concern about Greek debt restructuring and broader economic weakness prompted investors to book profits, opening the way to further declines as the index broke a recent support level.

Banks, exposed to euro zone sovereign debt, sold off on rumours - swiftly denied by officials - that Greece may seek to extend its March 8 deadline to convince its private creditors to take part in a bond swap.

Athens has secured an international bailout but still faces many hurdles as it strives to avoid a chaotic default. Investors are likely to remain jittery about the impact across the rest of Europe until the debt swap is done.

The markets, in fairness, are no longer excessively cheap and so some money is coming off the table, Gerard Lane, equity strategist at Shore Capital, said.

By 12:23 p.m., the FTSE 100 was down 62.42 points, or 1.1 percent, at 5,812.36, in sight of an earlier intra-day one month low of 5,805.29 in early trade and on track for its biggest daily fall since January.

The FTSE sell-off accelerated after it dipped below 5,829, thus breaking out of the bottom of the range that has held since early February. This served to further darken the technical outlook which had started to build after the index broke through 10-, 20-, 30- and 40-day moving averages.

What we see here from the short term perspective does not look very promising, but it all depends on how we close today. A session close below both the mid-February low, and below the peak from January 26 would be increasingly negative, Dag Muller, technical analyst at SEB Bank, said, adding that such a close could pave the way for a correction to 5,746 to 5,651 area.

After a strong start to the year which saw UK-listed miners add 8.5 percent, analysts are starting to question whether much higher share prices are justified given the prospects of higher costs and possibility of softer demand.

Investors and corporates alike have been looking outside of Europe for revenues but with China - a key global growth engine and consumer of natural resources sold by many of the UK-listed firms - now looking to slow down its economy, that is also looking increasingly uncertain.

The weight of global concerns on the blue-chip index was underlined by its underperformance against the more domestic- focused small-cap equivalent <.FTSC>, which eased 0.5 percent.

There is a general feeling of a lack of commitment at these levels after what has been quite a positive first quarter. Chinese growth is starting to spook the market and there are questions over the euro zone and Greece, Dwight Burden, institutional salesman at Merchant Securities, said.

Implied volatility on the FTSE <.VFTSE>, seen as a crude barometer of investor risk aversion, rose 11 percent in its biggest one-day jump since late December.

At 20, the gauge implies that investors expect the average move on the FTSE 100 to be around 1.25 percent between the day's high and low -- roughly half as much as at the peak of volatility in September.

Russian precious metals miner Polymetal
topped the loser board with a 7 percent drop after UBS downgraded the stock to 'neutral', saying growth is largely priced in, while costs are likely to rise.

The FTSE 350 miners sector was down 1.3 percent, while industrial metals <.FTNMX1750> fell 3.5 percent and autos 3.3 percent.

Essar Energy and Cain Energy - both seen as likely candidates to leave the FTSE 100 in this week's reshuffle - were each down around 1.7 percent.

(Editing by Sophie Walker)