The agency, which is headed by Steve Radford, vice-chairman of the DMA Field Marketing Council, has been passed as fully compliant with the DMA's Field Marketing Best Practice Accreditation.
The accreditation scheme, which was introduced as a new industry benchmark in September, is designed to give field marketing practitioners and clients a recognised industry qualification for their work.
It expands on points made in the DMA Code of Conduct, which identifies 19 areas in which marketers can achieve higher standards.
IMS passed after an on-site audit by the DMA that looked at 57 different points, including client contracts, understanding client briefs and standards in campaigns.
Steve Radford, operations director at IMS, said: "Feedback from clients has been very positive. Of the clients surveyed in advance, all said that the scheme will make future purchasing processes and decisions easier.
"By selecting an accredited company, they can be sure that they are working with one of the very best field marketing providers."
The DMA's field marketing accreditation is the latest measure by the association to help raise standards within the direct marketing industry, and was created following an 18-month consultation period.