The Council of Ministers is the most powerful body in the EU. It is composed of national government ministers and must approve any new EU laws proposed by the Commission.
Its make-up changes according to the topic under discussion, so that agriculture ministers deal with farming issues, transport ministers with transport policy etc.
Each member-state is allocated a voting weight that reflects, to some extent, its population. At present Ireland has three votes, while the biggest four countries, Germany, France, Italy and Britain, have 10 each.
In practice, most decisions are worked out in advance by ambassadors meeting in the Council of Permanent Representatives (Coreper). If a vote is taken among ministers, the outcome is determined by a simple majority, a qualified majority or unanimity, depending on the policy area.
At present, a qualified majority is 62 votes out of a possible 87. But a blocking minority of 26 votes can defeat any measure.
The Nice Treaty changes the distribution of votes among the member-states. Put simply, smaller states double their present number of votes while the biggest countries triple theirs. Under the new system, Ireland will have seven votes and Germany 29.
Other changes include a requirement that decisions be approved by a majority of member-states and a "demographic safety net" where a majority must represent at least 62 per cent of the EU's total population.
The treaty increases the number of policy areas to be decided by qualified majority. Among the issues that will no longer require unanimity are some facets of justice and home affairs, the appointment of the Commission and the financial regulation of Cohesion Funds.
All aspects of taxation policy will continue to require unanimous approval.