In case Liberal Democrats v. European Parliament (Case 41/92) "the Liberal Democrats, a political party in Great Britain, (‘the applicant’), seek a declaration from the Court that the European Parliament (‘the Parliament’) has failed to act by its obligations under the first subparagraph of Article 138(3) of the EEC Treaty ( 1 ) and Article 7(1) of the Act concerning the election of the representatives of the Assembly by direct universal suffrage, annexed to Council Decision 76/787/ECSC, EEC, Euratom of 20 September 1976 ( 2 ) (‘the Act’) through its failure to submit to the Council a proposal for the election of members of the Parliament by a uniform procedure in all Member States".

These papers focus on the institutional reform of the European Union, especially on matters relating to the emergence of the directly elected European Parliament, the introduction of proportional representation (PR) to those elections, and the exceptional position of the United Kingdom. Mr Duff was Director of the Federal Trust in London and Vice-President of the Liberal Democrats, and advisor to successive leaders of that party on EU affairs, including on relevant negotiations with the Labour Party. He took a leading part in the activities of Group of the European Liberal Democrat and Reform Party (ELDR) in the European Parliament. He was elected MEP in 1999 until 2014 and served as coordinator of the Liberal Group on the Constitutional Affairs Committee throughout that time. He subsequently became a rapporteur on electoral reform.