The changes are detailed in guidance from the Quality Assurance Agency following a review of the external system, which is key to supporting academic standards.
The introduction of national selection criteria, which will form part of the forthcoming UK Quality Code for Higher Education, aims to ensure the competency of external examiners and to provide more consistency across the sector.
Until now, institutions have set their own standards on the recruitment and use of externals.
This had fuelled concerns that the system was too cosy and that the examiners were not always familiar with the subject areas they were overseeing.
In the new criteria, the QAA advises that externals should have proficiency in the field of study and relevant qualifications, and should not have conflicts of interest such as research collaborations with individuals involved in the programmes they are overseeing.
Tim Burton, assistant director in the QAA's Research, Development and Partnerships Group, explained that greater consistency would reassure universities and the public.
He acknowledged that the detailed guidelines could make it harder to recruit externals, but said that it would not always be necessary to meet every criterion.
In programmes requiring multiple external examiners, for example, some may be drawn from industry rather than academia, he added.
While such candidates would not have the same knowledge of higher education, he acknowledged, their industry experience would provide a valuable perspective to complement those of their academic peers - a view particularly beneficial in courses related to industry.
Another change is that students are to be provided with the name, position and institution of their externals, and will also have access to examiners' annual reports.
Asked whether this was symptomatic of an increasingly "consumerist" role for students, Dr Burton said that "everything we do at the QAA is informed by students and their needs".
He added: "External examining plays a vital role in institutions' quality management, so we wanted to ensure that we involved students...in developing the guidance."