* FTSE 100 down 0.2 pct
* Centrica hit by UBS downgrade
* FTSE down 0.4 pct since start of 2014
By Sudip Kar-Gupta
LONDON, Feb 18 A fall in heavyweight utility Centrica weighed on Britain's top equity index on Tuesday, which was unable to add to its recent two-week rally.
The blue-chip FTSE 100 index, which rose 1.1 percent on Monday, slipped 0.2 percent, or 14.01 points, to 6,721.99 points in early trading.
Centrica fell 3.3 percent, among the worst-performing FTSE 100 stocks in percentage terms, after investment bank UBS cut its rating on the stock to "sell" from "neutral".
Trading volumes in Centrica were already 25 percent of the stock's average 90-day volume - above those for the FTSE, where volumes stood at 8 percent of the index's average 90-day volume.
UBS wrote in a research note that increasing political scrutiny was impacting UK utility companies such as Centrica, which are under pressure over the prices they charge customers ahead of next year's general election in Britain.
"The UBS downgrade is adding more fuel on the downside for Centrica," said Dafydd Davies, senior trader at London-based Prime Wealth Group.
The FTSE 100 rose 14.4 percent in 2013 to post its best annual gain since 2009, but is down by 0.4 percent since the start of 2014 after global equity markets fell in January due to concerns over a slump in emerging markets economies.
However, the FTSE has steadily clawed back ground in February and has risen in eight of the last 10 sessions.
Hantec Markets analyst Richard Perry had a positive near-term outlook for the FTSE, with many investors expecting the UK stock market to rise slowly over the course of the year as the country's economic recovery gathers momentum.
"I'd be looking to buy into any correction. The general mood of the market is still to push higher," he said.