The objective of pressure groups and movements is to pressurize the government to agree to their demands. These groups try to get public support and sympathy for their objectives by carrying out campaigns, and some unconventional methods like organizing protests.
The relationship between political parties and pressure groups can take different forms. This can be either directly or indirectly. The pressure groups are either formed or led by leader of political parties or act as the extended form of political parties.
In most cases the relationship between parties and interest groups or movement groups is not direct. They often take positions that are opposed to each other, yet they are in dialogue and negotiation. Pressure groups with small public support backed by individuals willing to spend for the cause can hijack public discussion in favour of their narrow agenda.
In such scenarios the public interest groups and movements perform useful role of countering these undue influence.