LONDON (Reuters) - Outsourcing firm Serco (>> Serco Group plc) and Kazakh miner ENRC (>> Eurasian Natural Resources Corporation) will both leave Britain's top share index, FTSE confirmed on Wednesday, after share price slumps during a year beset with difficulties.

Serco has dropped 8.5 percent since the end of June after the UK government asked the police to investigate alleged fraudulent behaviour by Serco staff working on the outsourcer's contracts.

Kazkh miner Eurasian Natural Resources Company is down 22.2 percent year to date, and leaves the index just as its founders finalise plans to take it private after six years in London, marred by corruption probes.

Energy services firm John Wood Group (>> John Wood Group PLC) is also relegated to the FTSE 250 mid-cap index <.FTMC>, while Greek coke bottler Coca Cola Hellenic (>> Coca Cola HBC AG), which switched primary listings from Athens in April, will join the FTSE 100 <.FTSE>, along with two other debutants, retailer Sports Direct (>> Sports Direct International Plc) and packaging firm Mondi (>> Mondi Plc).

Earning promotion to the FTSE 250 are Al Noor Hospitals Group (>> Al Noor Hospitals Group PLC), Entertainment One (>> Entertainment One Ltd), convenience food group Greencore (>> Greencore Group plc) and Partnership Assurance Group (>> Partnership Assurance Group PLC), while Anite (>> Anite plc), coal miner Bumi (>> Bumi PLC), JPMorgan Indian Investment Trust (>> JPMorgan Indian Investment Trust plc), Salamander Energy (>> Salamander Energy Plc) and Utilco Emerging Markets (>> Utilico Emerging Market Limited) all lose their mid-cap status.

The changes are implemented after market close on September 20, taking effect at the start of trading on September 23.

(Editing by Ruth Pitchford)

By Alistair Smout