The Democrat Party has accused former deputy national police chief Pongsapat Pongcharoen of involvement in the police station contract fiasco.

At the same time, Democrat spokesman Chavanond Intarakomalyasut blamed the Pheu Thai government for allowing a situation to develop in which hundreds of police stations remain unbuilt.

With three weeks to go before the election for Bangkok governor, Mr Chavanond said Pheu Thai candidate Pol Gen Pongsapat endorsed the terms of reference for the construction of the stations in 2009.

The terms allow the Royal Thai Police Office (RTPO) to give an advance payment of 15% of the construction price to the contractor. That action caused damage to the state, he said.

He demanded that Tarit Pengdith, director of the Department of Special Investigation (DSI), interrogate Pol Gen Pongsapat, whose main rival for Bangkok governor is the Democrats' MR Sukhumbhand Paribatra.

Earlier, Mr Tarit blamed former Democrat secretary-general Suthep Thaugsuban for the problem.

Mr Suthep was a deputy prime minister who supervised the RTPO when the office awarded the police station construction contract worth about six billion baht to PCC Development and Construction Co.

Mr Chavanond demanded Mr Tarit finish interrogating Pol Gen Pongsapat before the Bangkok governor election.

He said the Pheu Thai-led government had failed to ensure the contractor finished the construction on schedule.

The government granted three extensions of 60 days each to PCC, exempting the contractor from paying fines totalling 1.026 million baht.

Jirayu Huangsap, a Pheu Thai MP for Bangkok and Pheu Thai deputy spokesman, said yesterday the Democrat Party was refusing to take responsibility for damages resulting from the project.

"The Democrat Party is trying to find a scapegoat for this project and has chosen instead to attack Pol Gen Pongsapat, its rival for Bangkok governor," he said.

He said Pol Gen Pongsapat endorsed the terms of reference for the construction in 2009 when the Democrats were in government. Pol Gen Pongsapat did not do it alone but worked with a committee assigned by the then government.

He said it was not unusual that the current government allowed the extensions as the contractor had been affected by the extensive flooding in 2011.

Mr Jirayu asked the Democrats to stop the mudslinging and called for the public to monitor the case closely and seek the truth from Democrat party leader Abhisit Vejjajiva and Mr Suthep.

Earlier, deputy national police chief Pol Gen Worapong Chiewpreecha ordered the contractor to explain its spending of the advance payment of 877.2 million baht. Subcontractors have accused the company of failing to pay them for the construction of 396 police stations, which had forced them to stop work.

The contract allows the RTPO to demand an explanation and the contractor must provide it in 15 days.