The three men were convicted following the £23m Green biofuel trial, which was part of the Serious Fraud Office's investigation into Sustainable Growth Group, including its subsidiary companies Sustainable AgroEnergy plc and Sustainable Wealth (UK) Investments Ltd.
The biofuel products were sold to UK investors who invested primarily via Sipps.
Gary Lloyd West, former director and chief commercial officer of SAE, James Brunel Whale, former director, chief executive officer and chairman of SGG and Stuart John Stone, director of SJ Stone Ltd, a sales agent of unregulated pension and investment products, were convicted of conspiracy to commit fraud, conspiracy to furnish false information, fraudulent trading and Bribery Act 2010 offences at Southwark Crown Court.
Mr West was sentenced to 13 years' imprisonment, Mr Whale was given nine years and Mr Stone got six years, at the hearing in mid-December.
The SFO's criminal investigation focused on the selling and promotion of SAE investment products based on so called green biofuel Jatropha tree plantations in Cambodia. The green biofuel products were sold to UK investors who invested mainly through Sipps plans.
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These investors were "deliberately misled into believing that SAE owned land in Cambodia", that the land was planted with Jatropha trees, and that there was an insurance policy in place to protect investors if the crops failed.
Jane de Lozey, joint head of fraud at the SFO, said: "This is the first of a number of SFO cases to come to trial involving the mis-selling of investment products connected with Sipps in which savers on modest incomes have tried to invest for their retirement only to find themselves the victims of fraud.
"Pension scams can be difficult to detect even for experienced investors.
"The SFO is working closely with partner agencies across law enforcement to tackle this type of serious economic crime."
Director of the SFO David Green QC said: "These three individuals preyed on investors, many of whom were duped into investing life savings and pension funds. As a result, many lost life-changing amounts of money.
"This successful conclusion of the SFO's investigation clearly demonstrates the harm that this type of investment fraud has on victims and the SFO's ability and determination to bring criminals to justice."
His Honour Judge Beddoe described it as a "thickening quagmire of dishonesty... there were more than 250 victims of relatively modest means, some of whom had lost all of their life savings and their homes."
Mr West's and Mr Stone's charges and convictions under the Bribery Act 2010 are the first to be secured by the SFO since the act came into law in July 2011.
Both Mr West and Mr Whale were disqualified from being a director for 15 years while Mr Stone was disqualified for 10 years.  

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