This is one of the findings of a report published last week by the Better Regulation Executive.
The report, part of a series of reviews of national regulators, found that the GLA is doing a good job of improving the working conditions for some vulnerable workers.
However, it found that the authority could be broadening the number of partners it works with to help improve its intelligence gathering.
It stated: "The GLA has developed strong working relationships with a number of partners including the police, HM Revenue & Customs and the Health & Safety Executive, but could explore other potential sources of intelligence from other regulators working within the various agricultural sectors."
Chairman of the GLA Paul Whitehouse said: "We are continuing to focus on the rogues and support good businesses by dealing with those who illegally undercut them.
"Our work benefits those who try their best and comply with the law. These businesses are increasingly working with us to help protect workers.
"The report is very encouraging, but we know there is more we can do. We will be acting on the recommendations in the report."
The GLA was set up four years ago to regulate labour providers in the farming and the food industry - helping to improve the working conditions of vulnerable workers.