Offenders who commit antisemitic attacks backed by foreign powers such as Iran will face 14 years in prison under legislation to be included in the king’s speech next week. Shabana Mahmood, the home secretary, will be given the power under the National Security Act to designate proxy groups, such as those thought to be behind the recent attacks on the Jewish community, as a foreign intelligence service. Those carrying out activities on behalf of that group will face a maximum punishment of 14 years in jail even if they are unaware of who they are working for. The move is designed to tackle the growth of foreign proxies recruiting criminals on social media to carry out acts of terrorism, sabotage and espionage. The number of national security cases involving hostile states carrying out operations such as spying and sabotage in the UK has increased by half in six months, the head of counter-terrorism policing has said.…