The chasm between the Prime Minister and his Attorney-General appeared as wide as ever last night as Dominic Grieve reiterated his view that Britain has a legal obligation to consider granting voting rights to prisoners.

Within hours of Mr Grieve's evidence to the Justice Committee on Wednesday, that the UK risked damaging its reputation if it ignored a European Court of Human Rights judgment that it must lift a blanket ban on electoral rights for inmates, David Cameron had dismissed the suggestion.

But last night, giving the keynote speech at the BPP Law School, Mr Grieve, pictured, said that although the ultimate decision lay with Parliament, which was not subservient to the Strasbourg court, "observing its judgments is an international legal obligation... It is possible for Parliament to take no action on the judgment, although that would leave the Government in breach of the Treaty and liable to criticism and sanctions from the Council of Europe by its fellow signatories and to damages awarded by the Court"/