Danny Alexander has said no-one should face a cut in state help if no suitable smaller property is available and all disabled claimants should be exempt.
In a direct message to the Conservative government, the Chief Secretary to the Treasury said the Liberal Democrats will "make the case for these new fairer rules."
Speaking to The Mirror he said: "If we can't convince our Conservative coalition partners, we will commit to these reforms in our 2015 manifesto."
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The video, obtained by ITV News, shows scores of migrants desperately trying to board lorries in a restricted area within the tunnel.
Ex-Spitfire pilot Allan Scott, 94, said he was told off by the Queen when he first met her in 1943 when she was just 16.
Last minute preparations are going on at the Church of St Mary Magdalene where Princess Charlotte will be christened.