"I think they [investors] are already duped or cheated," the Guardian newspaper quoted Mr Mitvol as saying.
"I don't think we have to wait for a big crisis to occur in order to see this problem.
"When a proprietor-licensee has data which can be different from the state data, this is firstly abnormal and secondly a fraud. I can add that soon there will be results of our work with one company announcement which will significantly reduce reserves."
Mr Mitvol said he wanted to see greater cooperation between Russian and British regulators over reserves statements.
Click here to run an energy price comparison, and see if you could be paying less for your gas and electricity.