In almost all liberal democracies, there are several organized groups representing the various interests of its citizens. They interact among themselves and with the government. The presence and role of specific interest groups augment and supplement the role and purposes of the political parties. They are the part of a wider political process.
While parties are formal, open and are recognized part of the political system competing for power the interest groups are informal, often secretive, concealed and conspirational and sometimes even unrecognized entitles.
Pro.Finer refers to them as ' anonymous empire' others have called them 'invisible government' and 'unofficial government'
An interest group represents the social, economic and political interest of a particular segment in the polity like farmers, industrial workers, miners, business and commerce, or professional group like medical practitioners, lawyers, teachers, youth and students etc. its members have common objectives and share certain similar values.
They try to build public opinions in their favours and often canvas support of party leader, legislature and government officials, in pursuance of their objective.
1. Associational Interest Groups
2. Institutional Interest Groups
Examples are trade unions, chamber of commerce and industry, shopkeeper's association and lawyer organization etc.
Examples are service organizations like defence, police and civil service personnel, employees in educational institutions and
scientific laboratories and public sector units.
Set up for a specific temporary demand demand and transient interest, which is terminated on he attainment of its objective, like Vishal Haryana movement, settlement of water dispute between Andhra and Tamilnadu, settlement of boundary dispute between Karnataka and Maharashtra etc.
The method and functional style of interest groups vary in different political systems conditions by five factors.
1. Pattern of political institution
2. Nature of party system
3. Political culture and attitude of leaders and people.
4. The nature of issues and problem concerned
5. The character the type of the concerned interest groups. Different types of party systems give rise to different form of interest group activities. In counties were party system is weak, the interest groups work on their own. In some countries these groups have closer relationship with the political parties. The work of interest group is determined by the political culture of the country. Every interest group by its own nature and characteristics employs different approaches, methods and tactics.
Influence that interest group can exercise depends upon the several important factors like its own organizational strength, discipline and perseverance of its members in pursuing and issue.
Money is used by interest groups for legal and illegal activities. It is required to promote public relation campaign, and of using the media to popularize the issue. Payments of bribes to vulnerable officals, ministers, political parties, legislatures etc., are not unknown methods of pressurizing.
Interest groups that work for larger human causes like peace, disarmament, environmental protection, de-segregation and racial equality, human rights decolonisation etc, pursue a different approach and method. They work by building enlightened public opinion, by promoting an all-party consensus, by enlisting the sympathy, good sense and compassion.
To sum up, unlike political parties, interest groups do not work for capturing power. Their objectives are limited and specific. They provide necessary link in functioning of democracy.