Bangkok: Thailand's newly appointed Prime Minister Somchai Wongsawat faced a formal complaint by a Thai senator on Monday, alleging he had broken the constitution by owning shares in a company that holds a concession from a state firm.

Ruangkrai Leekijwatana, who toppled Somchai's predecessor, Samak Sundaravej, with a similar legal challenge, filed his complaint with the Election Commission but said he would also ask the Constitutional Court to look into it.

"I want the Election Commission to investigate if the prime minister should be disqualified for violating the constitution," he told reporters.

The complaint focuses on Somchai's share in Internet company CS Loxinfo, which has a long-term deal with state telephone firm CAT Telecom to provide satellite Internet services.

According to the 2007 constitution, any elected politician is barred from holding shares in a company that has a contract with a state firm.

Somchai, who is also Thaksin's brother-in-law, brushed off the allegation.

"Before I took this job, I strictly followed every law," he told reporters on Sunday after a hostile reception from an anti-government crowd at a Bangkok shopping mall.