pbr David Cameron has made a last-ditch attempt to win support for Government plans to treble university tuition fees ahead of a crunch vote.br ppbr The Prime Minister insisted the proposals are "sustainable, competitive and fair" as he acknowledged the "passion" of those opposing his plans.br ppbr Students and lecturers have already begun staging a fresh round of demonstrations and sit-ins ahead of Thursday's crucial vote on controversial proposals to charge students fees of up to £9,000.br ppbr Union leaders accused Mr Cameron of failing to fully understand the impact his Government's plans will have on universities and students.br ppbr As tension over the looming vote grew earlier, Mr Cameron and Labour leader Ed Miliband traded verbal blows in the Commons, and ministers announced new concessions aimed at heading off a major backbench rebellion.br ppbr In a speech in east London, Mr Cameron insisted that passion surrounding this issue was "drowning out some of the truth" about the package on offer.br ppbr He said the plans would widen access to university, create incentives to improve the quality of courses and leave the poorest graduates better off than under the existing system. Current funding arrangements are "unsustainable, uncompetitive and unfair", Mr Cameron added.br ppbr There were heated clashes during Prime Minister's Questions as Mr Miliband accused the Prime Minister of being "out of touch with ordinary people" - highlighting his privileged education at Eton and Oxford.br ppbr Amid speculation that half of Liberal Democrat MPs could rebel tomorrow, the Labour leader insisted the coalition was "in chaos". Mr Cameron hit back at Labour's "rank hypocrisy" on university funding, saying that the Government's proposals meant the poorest would pay the least.br ppbr Business Secretary Vince Cable announced further concessions aimed at easing the financial burden on poor students in a fresh bid to win over doubters.