Britain's highest court, the House of Lords, yesterday dealt a blow to the government's anti-terrorist legislation by making it harder to prosecute under a law which makes membership of a proscribed terror organisation a criminal offence.

The law lords ruled that requiring defendants to prove that the organisation was not proscribed when they joined and that they had not taken part in its activities since it was proscribed - a reversal of the usual burden of proof - violated the presumption of innocence guaranteed by the European convention on human rights.