LONDON (Reuters) - Outsourcing firm Serco (>> Serco Group plc) is set to exit Britain's blue chip share index in a reshuffle this week that could also see the demotion of troubled Kazakh miner ENRC (>> Eurasian Natural Resources Corporation).

Greek coke bottler Coca Cola Hellenic (>> Coca Cola HBC AG), which switched primary listings from Athens in April, is poised to join the index on Wednesday, along with retailer Sports Direct and packaging firm Mondi (>> Mondi Plc).

It is unclear who other than Serco will be demoted but ENRC is a strong candidate following a poor performance this year, even before its founders finalise plans to take it private after six years in London, marred by corruption probes.

That would leave no former Soviet mining companies in the top index following the exodus of Polymetal (>> Polymetal International PLC) and steel producer Evraz (>> EVRAZ plc) in the last reshuffle in June and Kazakhmys (>> Kazakhmys plc) in March, as the sector has been hit by slowing demand, corruption probes and regulatory inquiries.

Indian miner Vedanta (>> Vedanta Resources plc), industrial firm AMEC (>> AMEC plc) and energy services firm John Wood Group (>> John Wood Group PLC) are also in the frame for demotion to the FTSE 250 mid-cap index <.FTMC>.

Trading volumes and volatility in the stocks likely to move can jump in the days around the reshuffle as pension funds, exchange-traded funds and investment trusts with FTSE 100 tracker products re-weight their portfolios.

Serco's share price slumped 10 percent in the third quarter after the UK government said it would not award the company any new contracts and would review existing ones following news of alleged fraud in their prisoner escort contract.

The firm, which was already one of the smallest stocks in the FTSE 100 <.FTSE>, is now the 117th biggest UK-listed company by market capitalisation, based on its closing price on September 6.

Any company falling to 111th position or below is automatically deleted from the FTSE 100 and added to the FTSE 250 <.FTMC>. Any company rising to 90th position or above is automatically added to the FTSE 100, according to FTSE rules.

MONDI SET FOR PROMOTION

Coca Cola HBC (>> Coca Cola HBC AG) is poised to join the FTSE 100 after shifting its main listing to London and could see demand for around 13.7 million shares in September from those looking to reweight their funds, according to Societe Generale data.

Although currently not ranked in any FTSE indexes, its market capitalisation of $10.65 billion makes it the 58th biggest company in the UK, comfortably qualifying it for FTSE 100 membership.

It should be joined by Sports Direct (>> Sports Direct International Plc), Britain's biggest sports retailer. It is now the 81st biggest company by market cap after its share price jumped to all-time highs following a 40 percent surge in annual profit, helped by signs of recovery in the UK economy.

South African paper maker Mondi, as the 87th biggest UK-listed stock, also looks set to make it to the premier listing for the first time, boosted by a 48 percent jump in first-half earnings, which has helped its shares rally 31 percent since the end of June.

(Editing by Susan Fenton)

By Alistair Smout