State experts are poring over the legality of Khunying Pojaman Shinawatra's controversial Bt772-million purchase of land on Ratchadaphisek Road in Bangkok.

The wife of deposed premier Thaksin may face prosecution and the government could repossess the prime plot, a source said yesterday.

"The central legal question is whether Pojaman is eligible to be involved in the transaction in light of bans on office holders entering into business deals with the state," the source said.

As the wife of a prime minister, Pojaman might have not been legally entitled to buy the plot - which was government property - the source added.

An Assets Examination Committee (AEC) subcommittee is investigating the transaction.

Pojaman bought the plot in 2003 from the Financial Institutions Development Fund, the government's financial-rescue arm.

Under anti-graft law, prime ministers and other Cabinet members cannot enter into business contracts with the state.

Moreover, Article 122 of the Counter Corruption Act stipulates the ban on Cabinet members applies to spouses as well. The ban covers equity stakes in companies engaging in joint ventures with the government.

The subcommittee will determine whether this provision is applicable to the Pojaman transaction.

In a related development, AEC member Viroj Laohaphan has enlarged his tax-audit panel to 10 to speed up checks on tax liabilities arising from the Shin Corp sale.

"The deal is complex and needs many tax experts for a thorough audit," he said.

Viroj said each panel member would focus on a particular aspect before drawing together the big picture of the deal and its tax obligations.

Colleague Sak Korsaengruang said he suspected foul play, even though the deal appeared to be by the book.

"So many lawyers and advisers were involved in putting the deal together. The AEC will have to mobilise high-calibre tax professionals to smoke out any offence," he said.

Sak promised the AEC would get to the bottom of allegations concerning all Thaksin and former government-minister corruption under investigation.

The AEC is determined to fight alleged corruption and policy abuse in the previous government, he said, dismissing speculation that investigations would be rigged.

"The AEC will not compromise its integrity," he insisted, adding that Pojaman could not influence the probe, referring to her recent meeting with Privy Council President General Prem Tinsulanonda.

AEC chairman Nam Yimyaem pleaded for time to uncover evidence of graft, citing complex legal issues.

"The proceedings will take time and the AEC is trying to go after former ministers, who are the real masterminds," he said.