* FTSE 100 down 1.0 percent
* Banks weak on Europe debt concerns, tax fears
* Oils weak; BP falls on oil slick worry
By David Brett
LONDON, June 8 (Reuters) - Britain's top shares were lower by midday on Tuesday, as Europe's debt troubles and the threat of punitive taxes hit banks, while BP's <BP.L> Gulf of Mexico oil disaster dragged on the stock and sector sentiment.
By 1123 GMT, the FTSE 100 <
> was down 51.76 points, or 1.0 percent, at 5,017.30, having recovered from an intraday low of 4,990.60.UK-focused banks were poor performers as twin worries over euro zone debt exposure and the threat of possible levies on lenders hung over them.
European finance ministers sought agreement on Tuesday on how to make banks pay for financial crises. [
]Lloyds Banking Group <LLOY.L>, Barclays <BARC.L> and Royal Bank of Scotland <RBS.L> fell 1.4 to 2.4 percent. However, global banking giant HSBC <HSBA.L> added 0.3 percent, helping limit the sector's overall fall.
Meanwhile, in a direct warning to British investors, ratings agency Fitch said the UK faced a formidable fiscal challenge, sending the cost of protecting British government debt against default higher. [
]"Growth is going to hard to achieve anyway, (that) coupled with austerity measures all round Europe have resulted in an almost inevitable double-dip recession," Jeremy Batstone-Carr, head of research at Charles Stanley said.
Debt fears have cost Britain's blue-chip index around 800 points, or 13.8 percent, since mid-April.
COMMODITY RETREAT
Energy shares were the biggest blue-chip fallers, led by BP <BP.L> as the oil spill crisis in the Gulf of Mexico, along with global growth issues, drained confidence from the sector.
BP was down 3.9 percent, while peers Royal Dutch Shell <RDSa.L> and BG Group <BG.L> lost 1.4 and 1.5 percent respectively.
Miners pared an early rally, spurred by investors on the hunt for bargains, as macroeconomic worries took their toll fuelling concern about demand. Kazakhmys <KAZ.L>, Rio Tinto <RIO.L> and Vedanta Resources <VED.L> dropped 1.0-2.2 percent.
Among individual fallers, Tesco <TSCO.L> shed 2.8 percent as investors reacted uncertainty after Terry Leahy, the retailer's long-standing boss, announced his surprise resignation.
Tesco said he will be succeeded by lifelong company man and head of international business Philip Clarke.
On the upside, the top gainer was power generator rental group Aggreko <AGGK.L>, up 3.5 percent, after it said full-year performance should be significantly better than expected as it benefited from contract wins including for the soccer World Cup.
Aggreko also benefited from hopes for a possible bid war at mid-cap peer Chloride <CHLD.L>, up 18.5 percent as investors bet that U.S. firm Emerson <EMR.N> could counter an agreed takeover offer for the British firm from ABB <ABBN.VX>.
Takeover interest also saw blue-chip security firm G4S <GFS.L> climb 1.8 percent higher, extending gains made in the previous session.
The Daily Mail's Market Report on Tuesday cited revived rumours that a private equity consortium led by Kohlberg Kravis Roberts is lining up a 5.3 billion cash offer worth 375 pence a share for the security provider.
(Editing by Erica Billingham)