By Atul Prakash

LONDON (Reuters) - The blue chip share index jumped 1.2 percent on Thursday, its strongest showing in six weeks, as rebounding banks and mining stocks offset a slump in Carphone Warehouse (CPW.L: Quote, Profile, Research) and weaker retailers.

The FTSE 100 .FTSE gained 67.2 points to end at 5,790.5, its biggest percentage daily gain since May 2, helped by U.S. data that showed surprising strength in consumer spending.

Traders said short-covering contributed to a 9.7 percent rise in bank HBOS HBOS.L, while Barclays (BARC.L: Quote, Profile, Research), Royal Bank of Scotland (RBS.L: Quote, Profile, Research), HSBC (HSBA.L: Quote, Profile, Research) and Lloyds TSB (LLOY.L: Quote, Profile, Research) gained between 1.5 and 7.9 percent.

Standard Chartered (STAN.L: Quote, Profile, Research) rose 6.9 percent to feature among one of the leading FTSE 100 gainers after Goldman Sachs upgraded the bank's Hong Kong listing (2888.HK: Quote, Profile, Research) to "buy" as well as adding it to its Asia Pacific Buy List.

"It has been another very volatile day and we are just seeing a little bit of reaction to a couple of days of losses," said Roger Cursley, UK strategist at Investec.

"(But) It's difficult to see much strength coming through from the banks, given that we have got one rights issue to worry about in the form of HBOS. The economic outlook is far from rosy. We have slowing growth and rising inflation."

Miners also gained, with BHP Billiton (BLT.L: Quote, Profile, Research), Rio Tinto (RIO.L: Quote, Profile, Research), Vedanta Resources (VED.L: Quote, Profile, Research), Antofagasta (ANTO.L: Quote, Profile, Research) and Anglo American (AAL.L: Quote, Profile, Research) up between 0.7 and 4 percent.

"When we get a market which has been generally negative for so long, then obviously you are going to get days when you have a bit of bounce," said Peter Dixon, UK economist at Commerzbank.