In future, Whitehall departments will rely more heavily on mainstream media outlets rather than specialist TV and radio channels and journals when they target blacks and Asians.
The £366,000 "Commons Good" project, to be published in August, used in-depth interviews in people's homes and community centres, with Black Africans, Afro-Caribbeans, Orientals, Asians and mixed-race people. Two outside companies - Turnstone Research and Consultancy and Connect Research and Consultancy - were used.
Although many of the Government's campaigns were reaching ethnic groups, the research identified room for improvement. Featuring black and Asian actors in campaigns risked being seen as "tokenism" unless the cultural and lifestyle settings looked real. The study also identified a need for campaign materials to be in two languages rather than in separate publications since parents and children often read them together.
The research found that merely "running an ad on Zee TV" was not enough to reach the ethnic minorities. Many people, especially the younger generation, channel hopped and watched domestic TV and radio channels and read British journals as well as their own specialist ones.
Peter Buchanan, COI's deputy chief executive, said: "In future, we will be more confident about our ability to reach the ethnic minorities through the mainstream media. At the moment, we tend automatically to put some ethnic media on the schedule."
Buchanan said there were lessons for private companies in the research.
"The ethnic minorities are a major group of consumers. But the commercial sector does seem to be dragging its feet about understanding them," he said.
The second area covered by the project was small- and medium-sized companies.
Jigsaw Research found that businessmen in small companies were sometimes unsure of where to get help and advice after government campaigns. Because the pressures of running their company were their main concern, they were reluctant to act on workers' rights - even when these were laid down by law.
The research findings will be made available to government departments and other public bodies and a website will be launched in September. COI hopes the study will allow the needs of ethnic minorities and small businesses to be "built in" when campaign briefs are drawn up, rather than added on later.
Catherine Blizzard, COI's director of research, said: "Many government campaigns are aimed at hard-to-reach audiences, but there is a lack of overarching information on specific groups.
"COI has a vast store of information, but each project is commissioned by a specific client in relation to a particular campaign."
She said budgets did not allow the research needed to examine audiences in depth.
Alan Bishop, COI's chief executive, said the project demonstrated how the Government could "lead the market". COI now plans to carry out similar research on socially excluded people and about new technology.