The family of British activist Tom Hurndall have demanded a meeting with the British government after the Israeli authorities announced the early release of the soldier who killed him.

Taysir Hayb will be freed next month after serving six years of his eight-year sentence, after a ruling on Monday by the Kastina military court in southern Israel.

Hurndall was shot in the head in April 2003 as he was helping Palestinian children to cross a street in Rafah, Gaza.

Hurndall's father said yesterday he was not surprised by the early release of Hayb, who he said had been treated as a scapegoat by the Israeli army. He is asking for a meeting with the foreign secretary, William Hague, and the attorney general, Dominic Grieve, to put greater pressure on Israel over civilian deaths.

"Taysir was part of a policy and was not the principal culprit," Anthony Hurndall said. "The issue is that the Israeli army are uncaring of civilian safety."

Hayb was convicted of Hurndall's manslaughter in 2005 after claiming he was shooting at an armed Palestinian. He later admitted that was a lie. A month before Hurndall's death, American activist Rachel Corrie was killed by an Israeli army bulldozer in Gaza. James Miller, 34, a British cameraman, was shot dead in Gaza in May the same year.

Hurndall, a 21-year-old activist, had been filming with the pro-Palestinian International Solidarity Movement when he was shot. He died in London after nine months in a coma.

In a statement the Foreign Office said: "We note the court's decision to release Taysir Hayb and recognise the grief this decision will cause to the Hurndall family. We have the deepest of sympathies for the Hurndall family. Tom's death was a tragedy."

Anthony Hurndall described the statement as tame. He said: "I would like them to say that this is not just a tragedy but that the Israeli government is directly responsibility for Tom's death and should acknowledge this and take steps to put matters right by changing policies to ensure that civilians are not shot or killed indiscriminately. I'm disappointed; they could have said it more forcefully."

He added: "We would now like a meeting with William Hague and the attorney general. That rather weak response should act as a trigger to a meeting. We want the British government to help ensure that senior officers are bought to account and prosecuted."

Mr Hurndall, a former property lawyer who took up his son's case, added: "There are so many accounts of civilians being killed deliberately for no immediate military benefit. It's gone on for 10 years and it is deeply callous. We came to this situation with open minds but the more we have investigated the clearer it has become that this is an inhumane and brutal policy."

Speaking for the Hurndall family, he said: "We are not anti-Israeli or pro-Palestinian. Our deep concern here is that nothing is going to happen to resolve issues between the Israel and the Palestinians unless there is a degree of honesty and fact-facing and balance restored.

"War crimes have been committed and continue to be committed in Gaza."Hurndall's sister Sophie told Israel's Ha'aretz newspaper that she was "angry and shocked" by the early release of Hayb. But she said she blamed the Israeli military rather than Hayb.

"It's about the system. Not the man himself," she told Haaretz. "This man who shot Tom was the same age as him. He is both the victim and the killer. He is part of a system that proactively encouraged soldiers to target civilians."

Hayb's lawyer welcomed the decision. "At first, we found it hard to believe that the committee will have the possibility and the courage to face great international pressures not to release him. Eventually, we are happy that the committee made the right decision, giving priority to Taysir's rehabilitation and return to civil society."

After the hearing Hayb said: "I feel regret and I am sorry for what has happened ... We cannot bring the person back, but we must not bury the person that committed the crime. Okay, there was a mistake, I understand what happened, but I also did time in prison ... The case and the deceased will stay with me for the rest of my life."Hayb was also convicted of obstruction of justice, giving false testimony and soliciting false testimony.

Last night a Foreign Office spokesman said: "We lobbied the Israeli government extensively on this issue following Tom Hurndall's death. Since the news of Taysir Hayb's release emerged, we have been trying to establish the reasons why he has been released early. We have today raised it with the Israelis through both the Ministry of Foreign Affairs in Tel Aviv and the Israeli Embassy in London. We will press them for an immediate response on this issue.

"We will be in touch further with the family when we are able to give them a clearer picture. We can understand the distress that this news has caused and we are keen to provide a timely and accurate response based on a full understanding of the facts.

"As a general matter of policy, the UK is unequivocal about the need for Israel and the IDF to act with restraint and in line with international law, particularly in its conduct in the Occupied Territories."