ANGKOK (AFP) - Thailand's Opposition party on Wednesday lodged a motion of no-confidence against Prime Minister Samak Sundaravej, in a fresh challenge to his four-month-old government. The Democrat Party wants to grill Samak and seven members of his cabinet over their performance so far. The petition comes after state unions threatened to join ongoing street protests demanding Samak step down. "Even though just four months have passed, Samak's government has caused severe damage to the country due to inefficiency and disunity," the motion said. The motion also accuses Samak of mishandling soaring global oil prices and rising inflation, which have sparked threats of nationwide protests, and ignoring the crisis in the insurgency-hit south. Democrat Party whip Sathit Wongnongtoey said they hoped the debate could take place before the current parliament session ends on June 28, followed by a vote of no confidence. Deputy House Speaker Somsak Kiertsuranond, an MP with Samak's ruling People Power Party (PPP), said he would pass the motion to the house speaker, who would chose the appropriate time for the debate. If a simple majority of parliamentarians voted against the government, Samak would be forced to step down, although he could stall the motion by prolonging other debates, potentially until next year. Samak led the PPP to victory in December elections, which ended more than a year of military rule following Thaksin's overthrow in September 2006. After intense political haggling, Samak formed a coalition government in early February with five other parties. Between them they have 316 of the 480 seats in the lower house enough to survive the vote if the coalition sticks together. The motion against Samak and seven key ministers comes as the so-called People's Alliance for Democracy (PAD) continues for a third week to block a key thoroughfare in Bangkok's historic district. On Wednesday, 5,000 people marched to the foreign ministry to protest a deal with Cambodia on a long-disputed mountaintop temple that sits on their border. They fear the deal could benefit Thaksin, accusing him of seeking, via Samak, to profit from tourism at the temple. Foreign Minister Noppadon Pattama tried to reassure the protesters that Thailand would not lose any territory because of the deal reached with Cambodia, and said Thaksin was barely involved. "Thaksin had nothing to do with this issue, but cordial personal ties between him and Cambodia Prime Minister Hun Sen is likely to have contributed to its success," he told reporters.