Britain's FTSE falls for fourth day in row as Brexit fears grow

(ADVISORY- Reuters plans to replace intra-day European and UK stock market reports with a Live Markets blog on Eikon - see cpurl://apps.cp./cms/?pageId=livemarkets for site in development. See the bottom of the report for more details)

* FTSE 100 down for fourth day in a row

* Polls shows "Out" campaign lead widens in Brexit battle

* The Sun newspaper also backs Brexit

* Ashtead Group (LSE: AHT.L - news) rises on results

By Sudip Kar-Gupta

LONDON, June 14 (Reuters) - Britain's top share index fell for the fourth straight session on Tuesday after polls showed the campaign for Britain to leave the European Union had widened its lead ahead of next week's vote.

The FTSE 100 index was down by 1.6 percent at 5,951.39 points going into the close of trading, its lowest level in nearly four months. The index also fell below the 6,000 point mark for the first time since February.

A poll from TNS on Tuesday said the campaign for Britain to leave the European Union, or Brexit, had a "significant lead" over supporters of remaining in the bloc. The referendum will be held on June 23.

Britain's biggest selling daily newspaper, The Sun, also came out on Tuesday and urged its readers to vote in favour of leaving the EU.

"There is little enthusiasm to buy UK stocks before the referendum, and sentiment has been further dampened after The Sun backed the 'Leave' camp," said London Capital Group analyst Ipek Ozkardeskaya.

Economists have warned that leaving the EU would hit the British economy. That possibility has hit sterling in recent months and the FTSE has now started to track the general weakness in the pound.

While a weaker sterling can benefit the FTSE's international companies, it could also impact domestic consumer confidence in Britain.

"Domestic facing stocks, such as the housebuilders, look among those most at risk," said Dafydd Davies, partner at Charles Hanover Investments.

However, industrial equipment company Ashtead Group outperformed to rise 4.5 percent after a strong set of results and an announcement of a share buyback plan.

"This is a value stock worth investing in," said Gary Paulin, head of global equities at Northern Trust Securities, commenting on Ashtead.

ADVISORY- Reuters plans to replace intra-day European and UK stock market reports with a Live Markets blog on Eikon (see cpurl://apps.cp./cms/?pageId=livemarkets for site in development). In a real-time, multimedia format from 0600 London time through the 1630 closing bell, it will include the best of our market reporting, Stocks Buzz service, Eikon graphics, Reuters pictures, eye-catching research and market zeitgeist. Breaking news and dramatic market moves will continue to be alerted to all clients and we will continue to provide a short opening story and comprehensive closing reports.

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Mike Dolan, Markets Editor EMEA. (Additional reporting by Kit Rees; Editing by Susan Fenton)