
It also claimed Transport Minister Sophon Saram, who presented a set of elephant tusks to PM Abhisit Vejjajiva during a rest-stop at his residence, had violated the wildlife law.
"Abhisit, as prime minister and leader of the Democrat Party, has been in politics for 17 years and is in no position to claim innocence," Pheu Thai spokesman Prompong Nopparit said.
Prompong said he was disappointed that Abhisit appeared insensitive to the protected pachyderm, which was loved and revered by Thais.
He voiced confidence that any probe by the National Anti-Corruption Commission would see the PM convicted.
Politicians who violated the ban on accepting valuable gifts could face up to three years in jail and a fine up to Bt60,000, while people found to violate wildlife laws faced up to four years in jail and a fine of up to Bt40,000.
Democrat MP Thepthai Senpong said the prime minister and the main coalition party would abide by any NACC report. He reminding parties involved in the matter not to draw conclusions ahead of the probe outcome.
In a worst-case scenario, the gift would be returned if its valued exceeded the legal limit, Thepthai said.
Presentation of the gift was unexpected. It was a public incident that was not scheduled and happened suddenly amid a large crowd, he said. It was impractical to expect the prime minister to have gifts appraised every time someone gave him a memento, he said.
Social etiquette obliged the prime minister to make a gesture of accepting the gift before passing it to appropriate authorities to make a proper valuation, he said. A large number of gifts were returned following a proper valuation.
Penalties on such matters applied if an office holder deliberately took the gift as a personal possession, he said.
Sophon, meanwhile, said his family had been involved in raising domestic elephants for generations and that elephant tusks had been in his family's possession for more than 100 years.
He said he did not want to get involved in an attempt by the main opposition party to politicise the issue.
He admitted, however, that none of the elephant tusks owned by his family were registered with wildlife authorities.
Wildlife and plant protection division chief Wattana Wetyaprasit said the international convention on wildlife (Cites) prescribed a ban on possessing or trafficking tusks of African elephants. But it does not cover Asian elephants.