Phairoj said the Bt2.8-billion deal was agreed upon three years ago and approved by then labour minister Somsak Thepsuthin on September 7.

The Attorney-General's Office in its report did not recommend that the deal be dropped, just that the project value should be reduced even further, he said.

"Had I not signed it on September 28, people would have accused me of delaying the deal to extract 'tea money' from the vendor. Please be fair to me," he told reporters after defending the deal in a meeting with ministry officials.

The ministry never issued a statement hinting at the delay. It just informed him after he signed the deal, he said. "What could I do?"

Labour leader Wilaiwan-sae Tia said she would submit a request to Apai today for an investigation into the case, as well as other SSO projects including a "questionable" scheme using foreign traders to invest some of its Bt15.7 billion fund in stocks.