"This is an urgent call to Israeli society and its leaders to sober up and investigate anew the results of our actions," Breaking the Silence says.

Israeli officials insist troops went to great lengths to protect civilians, that Hamas endangered non-combatants by firing from civilian areas and that homes and buildings were destroyed only when there was a specific military need to do so.

Israel said the purpose of the 22-day operation that ended on 18 January 2009 had been to end rocket fire from Gaza aimed at its southern towns.

Palestinian rights groups say about 1,400 Palestinians died during the operation. Thirteen Israelis died in the conflict, including 10 soldiers serving in Gaza.

According to the UN, the campaign damaged or destroyed more than 50,000 homes, 800 industrial properties, 200 schools, 39 mosques and two churches.

Investigations

Reacting to the report, Israeli military spokeswoman Lt Col Avital Leibovich said:

"The IDF regrets the fact that another human rights organisation has come out with a report based on anonymous and general testimony - without investigating their credibility."

She dismissed the document as "hearsay and word of mouth".

"The IDF expects every soldier to turn to the appropriate authorities with any allegation," Lt Col Leibovich added. "This is even more important where the harm is to non-combatants. The IDF has uncompromising ethical values which continue to guide us in every mission."

There have been several investigations into the conduct of Israel's operation in Gaza, and both Israel and Hamas, the Palestinian militant group that runs the territory, have faced accusations of war crimes.

An internal investigations by the Israeli military said troops fought lawfully, although errors did take place, such as the deaths of 21 people in a house that had been wrongly targeted.

UN Secretary General Ban Ki-moon has requested more than $11m (£7m) in compensation from Israel for damage to UN property in Gaza. A limited UN inquiry blamed Israel in six out of nine attacks on UN facilities, resulting in casualties among civilians sheltering there.

Meanwhile, a fact-finding team commissioned by the Arab League concluded there was enough evidence to prosecute the Israeli military for war crimes and crimes against humanity, and that "the Israeli political leadership was also responsible for such crimes".

It also said Palestinian militants were guilty of war crimes in their use of indiscriminate rocket attacks on civilians.