London - Britain's top shares slipped at the open on Tuesday, dragged lower by heavyweight Vodafone after it was downgraded by Bernstein, and with traders citing some caution in the run-up to German sentiment data due later in the day.

The FTSE 100 was down 0.2 percent at 6,306.90 by 10:08 SA time, in what is expected to be a relatively lacklustre early session following Monday's closure of US markets for the President's Day holiday.

Mobile telecoms firm Vodafone fell 1.9 percent, taking around 6 points off the FTSE 100, after broker Bernstein cut its recommendation on the company to “underperform”.

Germany's ZEW survey, a gauge of investor and analyst sentiment in Europe's largest economy, due at 12:00 SA time, will fall under the spotlight.

Economists were expecting the index to have risen to 35 points this month from 31.5 in January.

“We... expect a quiet open till we see the ZEW from Germany that will dictate the trend for today,” said Atif Latif, director of trading at Guardian Stockbrokers.

Latif reckoned the index could dip to recent support, at 6,273, on a number below expectations and, on the flipside, to climb to 6,367, around recent resistance. - Reuters