Theresa May reportedly "took dictation" for her Brexit speech in Florence from the European Commission.
The Telegraph is reporting the Prime Minister had a number of consultations with EU officials over honouring the UK's membership commitments.
Mrs May's speech offered the European Union an additional £20bn to cover the budgetary costs to which the UK would have committed, had it elected to stay in the bloc.
EU sources and officials cited by The Telegraph claim the European Commission dictated this aspect of the Prime Minister's speech.
Furthermore, several aspects of the speech were reportedly discussed with EU counterparts before being presented to the Cabinet.
The negotiations over Brexit are set to continue later in the year.