Israel deported a Palestinian man to Gaza even though he faced almost certain execution there if caught by Hamas, which has charged him with spying for Israel, the man's lawyer said.

Details of the case emerged just days after Hamas, the Islamist rulers of Gaza, hanged three Palestinian men, one of whom had been convicted of the identical charge – collaboration with Israel.

Lawyers claim that Israel's Supreme Court ruled in favour of deporting O, a 28-year-old Palestinian man who had been living illegally in Israel with his wife and child, both of them Israeli citizens, in the knowledge that he could share a similar fate. Since his expulsion to Gaza last week, O is believed to have fled for Egypt, but it is thought that he will attempt to re-enter Israel to rejoin his family. His legal team, which denies the charges of collaboration against him, requested that the man be allowed to live with his family in the occupied West Bank.

For much of the past decade, O, originally from Gaza, lived illegally in Israel and the West Bank, but returned to the coastal enclave in 2006, where he was arrested and tortured by Palestinian security forces. He escaped when his detention centre was shelled by Israeli forces, but was later arrested in Israel for living there without a permit and was deported to Gaza in late 2010. Hamas on this occasion indicted him with spying for Israel, but he ignored demands to turn himself in and fled to Egypt.

When trying to return to Israel at the end of 2010, he was again arrested. But when he was due to be released last November, he realised Israel intended to send him to Gaza.