A Coalition source said the emails undermined the union’s credibility, saying: “It’s astonishing that Aaron Porter and the NUS should attack the Government’s proposals for being unfair when they propose to drastically cut support for low-income students.” Mr Porter said yesterday: “We were asked by Dr Cable [Vince Cable, Liberal Democrat Business Secretary] to demonstrate how fees could be kept at current levels and on the basis of his request we produced modelling to show how that could be done.