* FTSE 100 down 0.6 pct
* Index set for worst week of the year
* FTSE on a 9 session losing run
* ARM suffers from Liberum downgrade
By Alistair Smout
LONDON, Aug 21 (Reuters) - Britain's FTSE 100 hit an eight-month low on Friday, set for its biggest weekly loss since December after more weak data from China raised investors' concerns over weak global growth and possible deflation.
The FTSE 100 was down 0.6 percent at 6,327.42 by 0827 GMT. The index was down 3.3 percent for the week, set for its biggest drop in 2015 and hitting its lowest level since Dec. 17, 2014.
China's factories shrank at its fastest rate in almost 6-1/2 years in August, a private survey showed, hammering global stocks and commodity prices.
"There are many, and legitimate, contributing factors to the global economic slowdown narrative. These include China-related issues, such as the recent devaluation of its currency, the stock market's boom and bust in recent months, and slower GDP growth," Nigel Green, CEO of deVere Group, said.
"I believe that this volatility is likely to remain with us, at least until the end of the year ... But for most long term investors, fears of a near-term financial apocalypse are overdone."
Bucking the trend, precious metals miners rallied, buoyed as gold hit a six week high as investors sought safe havens.
The top faller was chip designer ARM, down 2.5 percent after a downgrade from Liberum, which highlighted a slowing demand picture for smartphones globally, including in China.
"Growth in the smartphone market has been the key driver of ARM's royalty revenue, in our view," analysts at Liberum wrote in a note that reduces forecast revenue for the next three years.
"The reduction is due to our view that the smartphone market is slowing." (Reporting by Alistair Smout; Editing by Alison Williams)