An alleged Russian spy who had an affair with Liberal Democrat MP Mike Hancock while working for him has won her appeal against deportation. The Special Immigration Appeals Commission (Siac) ruled Katia Zatuliveter, 26, should not be sent back to Russia. Miss Zatuliveter worked as a parliamentary researcher for the 65-year-old Portsmouth South MP. The Home Office said it was disappointed by the ruling. It said it stood by its original decision to deport her on national security grounds. In the judgement Mr Justice John Mitting, the chairman of Siac, said: \"Nothing in the material which we have analysed suggests, let alone demonstrates, that the appellant exploited her relationships for the purposes of the Russian state.\" The Siac hearing - most of which was held in secret - heard allegations she had been placed in his office because he was a member of the Commons defence select committee. But Mr Hancock insisted he had only had access to defence documents which were already in the public domain and denied passing any secrets to her. Met in St Petersburg Siac ruled Miss Zatuliveter had not been liaising with Russian spies from either the FSB or SVR agencies while working for Mr Hancock. Mike Hancock Mr Hancock denied he was in possession of defence secrets Miss Zatuliveter told the Siac tribunal she had met Mr Hancock in St Petersburg in 2006 and fell in love with him. She denied their relationship was based on sex and told the tribunal: \"I don\'t know how people usually have relationships but when I have a relationship, it\'s based on communication.\" A Home Office spokesperson said: \"National security is the primary duty of government and we will take all necessary steps to protect the public from individuals we believe pose a threat and remove them from the UK. \"The court ruled that there were ample grounds for suspicion. We are therefore very disappointed by the court\'s judgement and stand by our decision to pursue deportation on national security grounds.\" Sir John\'s judgement said: \"Her activities would have been of great interest to the FSB/SVR, but they are also entirely consistent with her being an ambitious young woman with an intense interest in politics and international relations. \"Further, they would have been of no use to the FSB/SVR unless their product was communicated to them, of which there is no open evidence.\"