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* Progress on Greek debt relief buoys European markets
* FTSE near 1-month high, up 0.7 pct
* M&S slumps after warning of short-term profit hit (Adds detail and updates prices)
By Kit Rees and Sudip Kar-Gupta
LONDON, May 25 (Reuters) - Britain's top shares indexclimbed on Wednesday towards its highest level in nearly amonth, lifted by gains at major banks and oil companies,although retailer Marks & Spencer slumped after atrading update.
The blue-chip FTSE 100 index was up 0.7 percent at6,265.18 points by 1409 GMT, near its highest level in around amonth.
Banks across Europe rose after the euro zone gave Greece itsfirmest offer yet of debt relief in what finance ministerscalled a breakthrough deal, under which the IMF will return totaking part in the bailout for Athens.
"There is some good news for investors as it looks like theymay not have to face another summer of high volatility withrespect to Greece," said Naeem Aslam, chief market analyst at TFGlobal Markets UK Limited.
Royal Bank of Scotland led the gainers on the FTSE100, rising 4.4 percent while peer HSBC Holdings alsoadvanced, up 3.2 percent.
Oil companies also rose as the price of oil edged towards$50 a barrel.
However, M&S slumped more than 9 percent, theworst-performing FTSE 100 stock in percentage terms as it headedfor its biggest daily loss since August 2008.
M&S warned of a short-term hit to profit as it pushesthrough a plan to turn around its underperforming clothing andhomeware business.
"We still have concerns that the company will not be able toreverse the declines in general merchandise (GM) like-for-likesales while the rate of growth in general merchandise grossmargins is likely to slow," Cantor Fitzgerald analysts wrote ina note, keeping a "sell" rating on M&S shares.
Product testing firm Intertek was also a notablefaller, down 5.7 percent and hitting a one-month low afterreporting softer organic growth.
ADVISORY- Reuters plans to replace intra-day European and UKstock 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 formatfrom 0600 London time through the 1630 closing bell, it willinclude the best of our market reporting, Stocks Buzz service,Eikon graphics, Reuters pictures, eye-catching research andmarket zeitgeist. Breaking news and dramatic market moves willcontinue to be alerted to all clients and we will continue toprovide a short opening story and comprehensive closing reports.
If you have any thoughts, suggestions or feedback on this,please email mike.dolan@thomsonreuters.com.
Mike Dolan, Markets Editor EMEA. (Editing by Toby Chopra)
