A coalition government is a government formed jointly by two or more political parties that agree to share executive responsibility. UK Parliament defines a coalition government as a government formed jointly by more than one political party and notes that coalitions can arise after a hung parliament when no single party has a clear working majority.
Coalition governments are particularly common where electoral systems produce legislatures in which no party is likely to obtain an overall majority, but they can also arise in majoritarian systems when election results produce no overall control or when parties voluntarily agree to share power. The essential feature is participation in government by multiple parties under an arrangement for joint governing. A coalition is therefore different from an informal parliamentary agreement in which one party governs alone while another party supports selected legislation without joining the executive.
Coalition governments require parties to negotiate how political authority will be shared. Coalition Bargaining can cover the prime ministership, cabinet portfolios, legislative priorities, budgets, appointments, parliamentary procedures, and mechanisms for resolving disputes. The resulting arrangement may be documented in a Coalition Agreement setting out shared policy commitments and rules for cooperation. The participating parties generally retain their separate identities and organisations, meaning that coalition government does not merge them into one political party.
Each party must balance collective governmental responsibility with its own electoral objectives. This creates a distinctive form of executive politics because coalition partners must cooperate in cabinet while continuing to compete electorally. The degree of cooperation required depends on parliamentary arithmetic, ideological differences, party discipline, institutional rules, and whether the coalition possesses a comfortable majority or depends on additional external support.
Coalition government should be distinguished from confidence and supply arrangements and other forms of parliamentary support. In a formal coalition, ministers from more than one party normally participate in the executive and share responsibility for the government. In a confidence and supply arrangement, a smaller party may support another party on confidence votes and financial legislation while remaining outside the cabinet. The House of Commons Library distinguishes formal coalition government from formal inter party agreements and confidence and supply arrangements.
This distinction matters because cabinet participation affects responsibility, policy influence, access to government information, and the ability of a supporting party to claim or avoid responsibility for government decisions. A government can therefore have substantial parliamentary support from another party without being a coalition government.
Coalition governments can provide a mechanism for translating fragmented electoral results into an administration capable of commanding legislative confidence. Where no party has a majority, the parties may determine that a formal coalition is preferable to minority government because it creates a more predictable legislative majority and allows participating parties to share executive responsibility. The UK coalition formed after the 2010 general election is a major modern Westminster example.
The election produced no overall majority, negotiations took place, and the Conservative and Liberal Democrat parties formed a coalition government on 12 May 2010. Earlier and later examples demonstrate that a hung parliament does not necessarily result in coalition government. The 2017 election instead produced a Conservative minority administration supported by a confidence and supply agreement with the Democratic Unionist Party.
Coalition government creates both advantages and constraints. It can broaden parliamentary support, reduce the likelihood that every legislative vote becomes a confidence crisis, and permit parties representing different electoral constituencies to participate directly in government. It can also require compromises that prevent either coalition partner from implementing its entire electoral programme. Cabinet decision making can become more complex when parties have different priorities or when coalition agreements leave certain issues unresolved.
Responsibility for unpopular decisions can also become contested because each party may seek to distinguish its own contribution from collective government policy. Coalition government therefore changes the structure of political accountability. Voters can evaluate both the governments overall record and the individual parties contributions, but assigning responsibility can be more complicated than under single party majority government.
Coalition governments vary according to their parliamentary strength. A coalition with a large legislative majority can normally survive without negotiating with external parties on every important vote, although internal disagreements can still be serious. A narrow coalition majority can make individual legislators and coalition factions more important because a small number of defections can threaten legislation or confidence.
A coalition can also operate as a minority if its participating parties collectively lack a majority, in which case it may require external parliamentary support. Coalition structure therefore cannot be inferred solely from the number of participating parties. The relevant questions include how many seats the coalition controls, whether those seats constitute a majority, whether confidence is guaranteed, how disciplined the parties are, and whether alternative governing arrangements are available.
Coalition governments are closely connected to hung parliaments but are not synonymous with them. A hung parliament means that no single party holds a majority, while a coalition government describes the executive arrangement that may follow. A hung parliament can produce a formal coalition, a minority government, a confidence and supply arrangement, or another inter party agreement. UK Parliament explicitly identifies coalition and minority government as alternative outcomes following a hung parliament. This distinction is essential because the electoral result and the governmental response are separate analytical questions. The election determines the parliamentary numbers, while subsequent Government Formation Negotiations determine how those numbers are translated into executive authority.
A common misconception is that coalition government means that the participating parties agree on everything. In reality, coalition partners normally retain different identities, policy objectives, electoral constituencies, and long term strategies. The purpose of a coalition agreement is to establish enough common ground to govern despite those differences. Another misconception is that coalition government is necessarily unstable. Stability depends on parliamentary arithmetic, party discipline, policy compatibility, leadership, institutional rules, and the availability of alternative governing arrangements. Coalition governments can be highly durable when the participating parties have strong incentives to cooperate, while they can become unstable when disagreements threaten core commitments or when coalition partners conclude that leaving government is electorally advantageous.
