Rapporteurs rely on secretariat officials to provide policy information that is independent from vested interests. They require this information to be provided quickly, so that lobbyists' policy claims can be verified ahead of the completion of the draft report. However, it turns out that officials' accumulation of specific policy expertise is endogenous to the lobbying process. Secretariat officials are generalists lacking the detailed policy information that they are called upon to supply. Entrenched interests including the Commission fill the void by providing officials with policy information and on occasion even loan them their experienced staff, thereby indirectly lobbying the rapporteurs. This activity directly affects the content of European Union legislation, as the information that rapporteurs receive and act upon is less independent than might have been expected. These ideas are analysed with the aid of over 150 structured interviews with policy actors, and with the aid of the results of an EP internal questionnaire.