Solid Energy declined to reveal how many workers it caught at each worksite, citing privacy reasons. It would also not say what drugs were detected.
"Releasing this type of information has the potential to reduce the effectiveness of the drug and alcohol testing regime which could subsequently affect the health and safety of all workers employed or engaged at our sites," said Mr Pope.
It caught 45 offenders in the year to June 30, 2012.
Mr Page said the company carried out 1773 random tests in the year to June 30, 2013, 475 fewer than the previous year.
The tests included pre-employment testing of employees, testing of contractors' employees before they worked on site, post-incident testing of employees and contractors, and random testing of employees and contractors.
- Westport News