FTSE on slide as China, Ireland dent sentiment

* FTSE 100 down 0.9 pct

* Banks drop; investors wait for clarity on Irish debt

* Commodities anchored as China raises reserve requirement

By Simon Falush

LONDON, Nov 19 (Reuters) - Banks led Britain's top share index lower on Friday, as lingering uncertainty on Ireland's debt dented the sector and China increased its reserve requirements, pressuring commodity stocks.

By 1146 GMT, the FTSE 100 <.FTSE> was down 49.47 points, or 0.9 percent, at 5,719.24, having closed 1.3 percent higher on Thursday. The index is down 1.4 percent for the week, on track for its worst such performance since late August.

Banks <.FTNMX8350> fell after Thursday's advance as investors retreated until a definitive solution is found to Ireland's problems.

A European Union and International Monetary Fund aid plan for Ireland is likely to come next week together with, or very shortly after, the release of Dublin's four-year austerity scheme, EU sources said on Friday. [ID:nLDE6AI0Y3]

China said on Friday it would raise banks' reserve requirements by 50 basis points, effective Nov. 29, the second time in two weeks.

"There was a weaker tone given what's going on in Ireland, and the (raised reserve requirement) will be the first in a range of steps the Chinese authorities will take over the next few weeks and months," said Michael Hewson, markets analyst at CMC Markets said.

Lloyds Banking Group fell 2.1 percent and HSBC was 1.8 percent lower.

"There's the prospect of some additional action in Ireland over the weekend, so I'm expecting a reasonably quiet day, with investors continuing to keep their risk positions pretty limited," Peter Dixon, economist at Commerzbank, said.

MINERS IN A HOLE

Mining stocks <.FTNMX1770>, fell on worries that China might adopt more stringent measures to add to the increased reserve requirements in order to keep inflation in check, including a drastic rise in interest rates.

Outsourcer Capita extended its decline from Thursday when it issued a trading update. It was down 3.5 percent, the heaviest faller among blue-chips, after an HSBC downgrade to "underweight".

On the upside, software firm Autonomy added 2.3 percent, with traders citing its analyst day on Nov. 29 as a potential catalyst and with sentiment surrounding the technology sector lifted by earnings-busting results from U.S. computer maker Dell .

Cairn Energy added 0.1 percent after India-focused mining group Vedanta Resources , down 1 percent, agreed a $6 billion financing deal with a consortium of banks to help fund its proposed acquisition of a majority stake in the Indian unit of Cairn Energy.

The next significant support for the index is at 5,682, a 50-day moving average which the index bounced off on Wednesday, Hewson at CMC Markets said.

(Additional reporting by Tricia Wright; editing by David Hulmes)