Brittan also emphasized that the member states of the EU have always had differing economic statuses. Financial aid within the EU helps countries develop, he added.
He named Ireland as the greatest success story in the EU.
The EU is considering admitting countries from Central and Eastern Europe into the economic and political alliance, he said.
"The test for potential [EU] members is not GNP or per capita income, but rather the potential for development of economic and political structures," Brittan said.
Brittan attributed the EU's success over the past 15 years to its single market economy which has eliminated barriers between member countries.
Brittan noted that a majority voting requirements has also helped the EU overcome a community that was "smothering with internal difficulties."