In 2007, Mr Anthony Herman Basil, 66, wrote to the Ministry of Manpower, Minister of Home Affairs and Security Industry Regulatory Department (SIRD), accusing the firm of supplying ill-disciplined and unfit guards.

He also alleged that Premier Security's managing director Saraj Din Sher Mohamed, and administration and finance manager Leow Cher Kheng had broken labour laws.

The firm and its two employees are now suing Mr Basil for defamation.

Premier Security, a leading security agency with some 500 guards, said that Mr Basil had acted out of malice after he was dismissed in December 2006.

Testifying in the High Court on Monday, Mr Saraj, 63, said that Mr Basil was hired in April 2006. He was fired because of consistently poor performance, he said.

As a result of Mr Basil's letters, SIRD conducted surprise checks on Premier Security's guards and found them to be 'alert, diligent and knowledgeable in their work,' Mr Saraj said.

Mr Basil is arguing that his letters are not defamatory as he had sent them only to those who were responsible to ensure the security of Singapore, and not to the newspapers.

He claims his complaints are true and he has raised them with the relevant ministries as they affect public safety.