Higher education watchdogs said gaps in quality control could lead to future problems with the franchised courses, which are worth billions of pounds to UK institutions.
Though most of the tens of thousands of students taking British degrees overseas were getting a "reasonable deal", some universities were relying more on luck than good practice to control standards.
They would need to introduce more rigorous procedures to ensure that qualifications issued by foreign institutions in their name were of the same quality as those taught in Britain, or risk triggering suspicion abroad that UK degree standards were slipping.
The study by the Higher Education Quality Council, which covered 20 overseas links in Greece, Hong Kong, Malaysia, Singapore and Spain, comes shortly after two British institutes not included in the sample ran into difficulties with foreign programmes.
Southampton and Swansea institutes of higher education were both criticised by the council this year for failing to ensure quality checks on degrees offered abroad matched the level of scrutiny at home.
The council's director of quality assurance Peter Williams said yesterday the survey had not uncovered any horror stories, "though that is not to say that horror stories don't exist".
UK universities, some of whom had set up partnerships only recently, were still on a learning curve, he said. "We did find good programmes but we also found a lot of what we would call variable practice - that is practice which we did not feel added up to security."
Most universities had failed to set out clearly enough in initial agreements with partner institutions overseas arrangements for checking standards and safeguarding the interests of students, the study found.
Responsibility for monitoring had often been left to individual departments in the home university, hampering quality control. Some universities had rushed into deals despite knowing little about a partner institution "to beat off potential competitors". In some cases, said the report, foreign governments had gained the impression that British universities relaxed entry requirements and standards for degrees offered abroad, triggering scepticism about UK higher education.
The council yesterday published a beefed-up code of practice, and is planning a series of "audit" visits next year.Reuse content