Thailand’s constitutional court on Thursday opted not to investigate the relationship between Prime Minister Thaksin Shinawatra and his family’s former company, a decision likely to fuel public frustration over the premier’s perceived lack of accountability.

The court voted 8 to 6 to reject the petition filed by 28 senators, which claimed the prime minister violated the country’s conflict of interest law by playing an active role in the affairs of Shin Corp, the telecommunications-to-airline conglomerate he founded.