The Intergovernmental Committee, headed by Paul-Henri Spaak, presented its definitive report on 21 April 1956 to the six governments of the member states of the European Coal and Steel Community.
The report formed the cornerstone of the Intergovernmental Conference on the Common Market and Euratom at Val Duchesse in 1956 and led to the signing, on 25 March 1957, of the Treaties of Rome establishing a European Economic Community and the European Atomic Energy Community.
The Spaak Report concluded that a sector-by-sector integration of the European economies would be difficult.
The integration of the European nuclear energy sector was desirable because of the costs involved, which surpassed the financial capacity of individual states.
The integration of electricity and fuel gas seemed irrelevant, as they were distributed solely at a national level.