During the debates held in the House of Commons on 14th March 2018 about the alleged poisoning of Russian spy Skripal in Salisbury, U.K. Parliament Foreign Affairs Committee Chair Thomas Tugendhat said (emphasis mine):
Will the Prime Minister also use the tools at her disposal to expose the wealth of the Putin family, given that $300 billion or more has been stolen from the Russian people by that man? We should expose him for what he is, and not be a useful idiot hiding behind the legalism of his crimes.
Is this an accurate estimate? If so, what documents it is based on?