* Charges related to airwave grants in 2002
* Charges include criminal conspiracy
* Bharti shares extend fall
NEW DELHI, Dec 21 (Reuters) - India's federal police filed charges against Bharti Airtel Ltd and Vodafone Group Plc's India unit on Friday as part of a probe into alleged corruption in the allocation of mobile phone airwaves a decade ago, a lawyer said.
The charges include criminal conspiracy, A.K. Singh, a lawyer for the Central Bureau of Investigation (CBI), told reporters. He said no executives of the companies were charged, but a former telecommunications ministry official was charged.
Shares in Bharti Airtel, India's top mobile phone carrier, extended losses after the charges were filed. The stock was down 2.9 percent at 0931 GMT.
A Bharti spokesman said he had no immediate comment, while a Vodafone India spokesman declined to comment. The companies have previously denied any wrongdoing.
The latest CBI probe concerns alleged irregularities in allotting mobile spectrum in 2002 during the previous government led by the Bharatiya Janata Party, which is now in opposition.
The investigation follows a scandal over airwave allocations in 2008 that rocked the ruling Congress Party-led government after a state auditor said the government may have lost up to $32 billion due to below-market price sales of radio spectrum.
Police have charged 19 people and three companies in that case and their trials are ongoing.
The Supreme Court had asked the CBI to investigate any possible irregularities in the granting of mobile permits from 2001 to 2007. The CBI estimated a potential loss of 8.46 billion Indian rupees ($154 million) in government revenue due to the alleged irregularities in 2002, Singh said.