An Explanatory Memorandum is prepared by the relevant government department to accompany each EU document. It sets out the Government's evidence about the general effect of the document which is then subject to the European scrutiny procedures of each House. This includes its financial, legal and policy implications, and any further relevant information, such as whether the document is awaiting further consideration by other European Community bodies. The explanatory memorandum must be produced within 10 days of depositing the document in the House.
Further information on this subject can be found from the following links.
House of Commons European Scrutiny Committee
House of Lords European Union Select Committee