FTSE slides on banks, commodities; M&S rebounds

* FTSE 100 down 2.1 pct, six gainers on the index

* Banks, commodity shares the standout losers

* M&S rebounds on market talk of bid interest

By Dominic Lau

LONDON, July 8 (Reuters) - Britain's top share index was down 2.4 percent by midday on Tuesday, tracking sharp losses in the United States and Asia on concerns that financial companies would unveil more writedowns and need to raise more capital.

By 1033 GMT, the FTSE 100 .FTSE was down 117.5 points at 5,395.8 after gaining 1.9 percent on Monday. The UK benchmark index has fallen 16.5 percent this year.

"When there is battle on the street and murder on the dancefloor, you've got to start buying. The market is probably going to start a bounce from here," said Manoj Ladwa, a senior trader at TradIndex. "We have been down to these levels before in the last six months and bounced off, although we are not poised for a major rally from here."

European shares were also down sharply.