Aaron Porter, president of the National Union of Students, will face leadership challenges from "hard Left" opponents who have called for a fresh wave of student mobilisation.

Members of the Education Activist Network (EAN) and the National Campaign Against Fees and Cuts (NCAFC) have pledged to stand for leadership posts under a "united Left" slate.

The groups, which are behind many recent protests and occupations, accuse Mr Porter of failing to mount tough opposition to rising tuition fees and funding cuts.

At a rally in Manchester on 29 January, Mr Porter had to be escorted to safety by police after being barracked by opponents. He later said that he had been subjected to anti-Semitic abuse. Mr Porter is not Jewish.

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Elections will be held at the NUS conference in April, with the result depending on delegate votes.

Mark Bergfeld, an EAN member and a master's student at the University of Essex, will be the united Left's candidate for president.

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He criticised the NUS leadership for supporting a graduate tax rather than "free education", a policy he said was part of its unsuccessful bid to gain a seat on the Browne Review panel. "If I were elected president, I would very simply say, the fight is not over. I'd encourage university students to occupy their colleges in defiance of the rise in tuition fees and call another national demonstration in central London," he said.

Michael Chessum, co-founder of the NCAFC and a University College London undergraduate, will be the united Left's candidate for vice-president (ÖйúAƬ).

Mr Chessum called for the NUS to address the "ideological clash between the market and the public sector as a means of funding education". He urged students to support wider campaigns by public sector workers against cuts by mounting "walkouts, occupations - it is about mass mobilisation and taking seriously the role of students as a physical force in politics".

The NUS released survey results showing student support for its campaign against higher fees.

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Of 1,258 students surveyed, 94 per cent were aware of the campaign. And 72 per cent said violence on the first NUS-backed demonstration has hindered the movement.

Mr Porter has criticised "hard Left factions" who "say we should be standing alongside those who kick in windows and burn effigies of Nick Clegg".

john.morgan@tsleducation.com