FTSE weakens, Next weather warning hits retailers

* Blue-chip FTSE 100 index dips 0.4 percent

* Retailers under pressure as Next (Other OTC: NXGPF - news) warns on weather

* Intertek up after hiring new CEO from Inchcape (LSE: INCH.L - news)

* AB Foods boosted by Credit Suisse (NYSE: CS - news) upgrade

* RBS (LSE: RBS.L - news) advances after cutting provisions for bad loans

By Tricia Wright and Atul Prakash

LONDON, Sept 30 (Reuters) - Britain's top share index dropped on Tuesday, with retailers falling after Next said it would have to lower its full-year profit forecast if the unusually warm weather continued.

The UK benchmark showed little reaction to data showing Britain's economy is bigger than previously estimated.

Britain's No. 2 clothing retailer fell 3.7 percent, the top blue-chip decliner in brisk trade, after saying the country's unusually summery autumn weather was deterring shoppers from buying winter clothing.

Its third-quarter sales to date were up 6 percent, lower than its previous forecast of up 10 percent. Trading volume in Next stood at 3-1/2 times its 90-day daily average, contrasting with the normal daily volume on the FTSE 100.

"Next does not often lower guidance. So the fact that they have said they may do so due to the warmer weather is hitting the shares, which have had a strong run, and will also hit the sector if the weather remains unseasonal," Securequity sales trader Jawaid Afsar said.

The weather warning put pressure on other retailers, with Marks & Spencer (Other OTC: MAKSF - news) falling 2.6 percent to be the second biggest decliner in the benchmark share index. Midcap Debenhams fell 1.8 percent.

The FTSE 100 was down 23.95 points, or 0.4 percent, at 6,622.65 points, by 1453 GMT. The index, which dropped 2.8 percent last week, is down almost 2 percent so far this year.

"We continue to highlight the bearish possibility of more downside given the increase in concerns over the last week," Accendo Markets head of research Mike van Dulken said.

Investors stayed cautious following soft manufacturing data from China, the world's biggest metals consumer, and civil unrest in Hong Kong, where tens of thousands of pro-democracy demonstrators extended a blockade of streets.

On the positive side, Primark owner Associated British Foods (LSE: ABF.L - news) topped the blue-chip leader board with a 4.6 percent advance after Credit Suisse lifted its rating on the stock to "outperform" from "neutral", highlighting that the discount fashion chain is now the key to the group's earnings.

Testing company Intertek jumped 2 percent after appointing a new chief executive to replace retiring chief executive Wolfhart Hauser.

Andre Lacroix will join from multinational car dealer Inchcape, where he has been chief executive since 2005.

Shares (Berlin: DI6.BE - news) in midcap Inchcape fell 3.4 percent.

Royal Bank of Scotland also notched up good gains after saying it will release a substantial amount from provisions it had set aside to cover losses on bad loans.

RBS rose 2 percent after the state-backed bank said it will release 800 million pounds ($1.3 billion) from provisions after an improvement in the economy, especially in Ireland (Other OTC: IRLD - news) . (Additional reporting by Sudip Kar-Gupta, editing by Mark Heinrich)