GuildHE and Million+ have fallen out over GuildHE's attempts to promote itself to the press. Both groups represent institutions committed to improving wider participation and they have one member in common.
But GuildHE, which speaks for colleges of higher education, and Million+, which represents post-1992 universities, do not always see eye to eye - as was obvious from a recent public exchange of e-mails between the head of each "mission" group.
The spat developed last week after the Higher Education Statistics Agency published the annual performance indicators, which show how well institutions have done in widening participation and preventing dropouts.
Based on its own analysis, GuildHE issued a statement to the media in which it said: "The latest performance indicators show that institutions represented by GuildHE ... are punching above their weight in their contribution to widening access to higher education.
"On average GuildHE institutions exceed their benchmarks for retaining their students better than any other type of institution - including the Million+ group of former polytechnics."
GuildHE argued that the more "intimate and supportive" environments of the small universities and colleges that make up its membership better suited students from disadvantaged backgrounds.
Pam Tatlow, chief executive of Million+, took exception to the statement, especially the reference to "former polytechnics". She expressed her displeasure in a publicly disclosed e-mail to Alice Hynes, the chief executive of GuildHE.
"Million+ is not a group of former polytechnics. Indeed some of our subscribing institutions were never polytechnics and more recently include some ex-GuildHE members," she wrote. "While the description of Million+ is inaccurate we also feel that we should discourage the press from using terminology of the 20th century when we and our students are in the 21st."
Ms Tatlow also expressed "concern" at GuildHE's focus on dropout rates. "Continuation rates by so-called mission groups are certainly not the area that we would encourage the press to emphasise ... given their treatment of this issue," she said. "When we discuss this with MPs and others, we do not ourselves compare performance on an interest group basis."
Responding to the criticism, Dr Hynes said: "I clearly had not appreciated that the 'polytechnic' word was troublesome in this way." She acknowledged that bald statistics could distort the complex reality of continuation rates and student trajectory through higher education.