The European Parliament has a range of supervisory and control powers. These allow it to exercise oversight over other institutions, to monitor the proper use of the EU budget and to ensure the correct implementation of EU law.
The President of the European Parliament has the right to speak at the start of each European Council, setting out Parliament's position on the subjects to be addressed by the heads of state and government.
After each summit the President of the European Council presents a report to the European Parliament on the outcome.
The European Council is made up of European Union heads of state and government, its president - elected for 2½ years renewable once - and the European Commission President. It defines the Union's general political direction and priorities.
At the beginning and end of each six-month presidency the President of the Council of the European Union discusses their programme with MEPs in plenary.
MEPs can table written and oral questions to the Council and can ask it to initiate new policies.
The Foreign Affairs Council is permanently chaired by the High Representative for Foreign Affairs and Security Policy. They, or a representative, attend plenary debates on foreign, security or defence policy. Twice a year, the High Representative reports to the European Parliament about these policies and their financial implications.
The Council of the European Union is the EU's other legislative body. It is made up of ministers from member states.
The European Parliament has the right to approve and dismiss the European Commission. Since 1994, commissioners-designate have been required to appear before an EP hearing. Under the Lisbon Treaty, EU heads of state propose a candidate for Commission President, taking into account the results of European elections. The candidate is elected by the EP.
The EP can censure the Commission and ultimately dismiss it. So far, none of the eight motions of censure brought before Parliament has been adopted. In 1999, the Santer Commission stepped down before Parliament forced its resignation.
The EP ensures democratic control over the Commission, which regularly submits reports to Parliament including an annual report on EU activities and on the implementation of the budget. Once a year, the Commission President gives a State of the Union address to plenary. Parliament regularly invites the Commission to initiate new policies and the Commission is required to reply to oral and written questions from MEPs.
The European Commission is the guardian of the treaties and the EU's executive arm.
Parliament can ask the Court to take action against the Commission or Council if they have acted in a way that is contrary to the spirit of EU law.
Parliament, together with Council, can ask the Court of Justice to set up specialised courts. For example, the European Union Civil Service Tribunal was established in 2005 to deal with disputes between the EU and its civil service.
The Court of Justice is the highest court in matters of EU law. It interprets and ensures equal application of EU law across all member states.
Parliament must be consulted before the President, Vice-President and Executive Board of the European Central Bank (ECB) are appointed by the European Council.
The ECB President presents the bank's annual report in plenary and takes part in a regular monetary dialogue with Parliament's Committee on Economic and Monetary Affairs.
The European Central Bank is responsible for conducting monetary policy for the euro zone.
The Court of Auditors presents the annual report on the previous year's budget to the Council and European Parliament. Based on the report, Parliament decides whether or not to approve the way the Commission handled the EU budget by granting the budget discharge.
Parliament must be consulted before the appointment of the members of the Court of Auditors by the Council.
The Court of Auditors audits EU finances. As an external auditor, it contributes to improving EU financial management and acts as the independent guardian of the financial interests of EU citizens.
Parliament elects the European Ombudsman. The Ombudsman reports back to the European Parliament and presents an annual report to MEPs. The Ombudsman may be dismissed by the Court of Justice at the request of Parliament in exceptional circumstances. The Ombudsman can start inquiries on his own initiative.
The European Ombudsman investigates complaints about maladministration in EU institutions and bodies.
Any EU citizen, resident, company or organisation can submit a petition to the European Parliament about EU law.
Parliament can set up a committee of inquiry to look into violations of EU law by member states.