Israel was strongly criticised by an all-party group of British parliamentarians visiting Gaza yesterday after its armed forces killed four Palestinians in two missile strikes during a new offensive against militants in the strip.

Israel was strongly criticised by an all-party group of British parliamentarians visiting Gaza yesterday after its armed forces killed four Palestinians in two missile strikes during a new offensive against militants in the strip.

Two boys, aged 14 and 15, died in a missile attack on Rafah, close to Gaza's border with Egypt, in another day of violence which began when an Israeli helicopter fired two missiles overnight into a group of Palestinians, killing a gunman and a 45-year-old bystander.

In a separate incident Hamas militants exchanged fire with Palestinian security forces in Gaza City after a car carrying armed men refused to stop for a police inspection. One Palestinian bystander was killed and 17 others were injured in the exchange.

Israel launched the offensive into Gaza late on Tuesday in response to a double suicide bombing earlier this week at the Israeli port of Ashdod that killed 10 Israelis. Israeli officials have also said they want to strike hard at militants ahead of a possible withdrawal from Gaza.

In a strongly worded attack on current Israeli policy, Baroness Williams of Crosby, the Liberal Democrats' leader in the Lords, John Bercow, the shadow International Development Secretary, and the senior Labour backbencher Joan Ruddock spoke of the "fear and anxiety" they had encountered among Palestinians on their 36-hour fact-finding trip, organised by the British and Irish charity Christian Aid.

Lady Williams was careful not to repeat the suggestion which cost her Liberal Democrat colleague Jenny Tonge a frontbench job, namely that she might have been a suicide bomber if she had been a Palestinian. But she said: "I wouldn't have used those words but I understand why she said what she said. I can see why young men with no job, no prospects, no way of providing for their family, are very easy meat for Hamas and others. I don't condone this. Nothing justifies blowing up innocent people but if we want to deal with the roots of terrorism we must be aware of the depth of unemployment and hopelessness in Gaza."

Mr Bercow told reporters: "The current stance of the Israeli government is unfair and will not produce peace. The current treatment of people in the West Bank and Gaza by the Israeli government is not justified."

Both went out of their way to emphasise their strong support for the existence of the state of Israel. Lady Williams's late husband Richard Neustadt was Jewish and Mr Bercow is a Jew who has visited Israel as a Conservative Friend of Israel.

The group, who are expected to see both Palestinian and Israeli senior politicians along with a group of British-Israeli families during their visit, condemned the decision of Israel's Prime Minister, Ariel Sharon, decision to cancel a planned meeting with the Palestinian Prime Minister, Ahmad Qureia, after the bombings in Ashdod.

* Israel's powerful defence establishment advised Mr Sharon yesterday to quit most of the Gaza Strip, strengthening his hand against rightists opposed to his go-it-alone plan, officials said.