The Tánaiste has accused Israel of the vindictive and collective punishment of the population of Gaza following an hour-long meeting with UN officials at the Rafah Crossing.
Micheál Martin said the Israeli Defence Forces was guilty of ongoing petty confiscations from aid trucks, including children's scissors, green sleeping bags and orange juice, on the basis that Israel regarded it as a "luxury" item.
He told reporters that this was collective punishment and Israel showing the Palestinians "who is boss".
While the volume of aid entering Gaza had increased at Rafah to the south, it was vital that a northern crossing was opened.
The Minister for Foreign Affairs said the ecosystem of aid was not functioning, in that flour shipments were pointless unless there was fuel for generators to bake bread.
He said UN staff were resigned to the prospect of an Israeli ground offensive on Rafah, where up to 1.7m Palestinians are currently seeking refuge.
Officials had described a situation of thousands of traumatised and unaccompanied children being looked after by adults who were themselves traumatised, he said.
Following his visit to the Rafah crossing, Mr Martin said it is "abundantly clear" that the humanitarian situation in Gaza remains "extremely grave".
He said that hunger was widespread and that infrastructure including health, sanitation and water systems have been destroyed.
"Despite this, Israel is continuing to impose unacceptable restrictions which impede a comprehensive humanitarian response in Gaza," he said.
The Tánaiste said a "properly functioning deconfliction system" and full access for humanitarian aid to northern Gaza was "essential".
He warned that an Israeli military operation in Rafah would have "disastrous humanitarian consequences" for the 1.5 million people sheltering there.
Mr Martin said his visit left him in no doubt that "with almost the entirety of the Gazan population displaced, 100% of the population acutely food insecure, the north of Gaza facing famine and health and education facilities destroyed, what we are seeing is the collective punishment of a population for the crimes of Hamas".
Earlier, he said it was "very difficult to comprehend" what he called the "barbarity" of Israel's bombing campaign in Gaza.
He told a joint news conference in Cairo that there was no justification for the intensity of the campaign.
He referred to the attack on Sunday which killed 18 children, and the mass graves discovered at Khan Younis.
Mr Martin was speaking after a 90-minute meeting with Egyptian Foreign Minister Sameh Shoukry.
He said his fear was that when the war ended, the loss of life would be much worse due to what might be discovered under the rubble of Gaza.
Mr Martin said the world had to call a halt to the kinds of warfare that levelled cities, such as in Syria, Ukraine and Gaza.
Both men discussed plans by Ireland and a number of EU member states to recognise the State of Palestine.
Mr Martin said such a move would provide encouragement to the Palestinian Authority and the Palestinian population.
He said the vote at the UN General Assembly in May on inviting Palestine to join the United Nations could provide a new context to the joint recognition at EU level.
Mr Shoukry accused Israel of attempting to "liquidate" the Palestinian presence in Gaza.
Speaking earlier, Mr Martin welcomed the Colonna report into the United Nations Relief and Works Agency for Palestine Refugees and said Israel had deliberately tried to undermine the organisation for political reasons.
He said the report had made it clear that UNRWA was "indispensable and irreplaceable".
But on the specific allegations of complicity in the Hamas-led attacks, the report said that Israel had not provided the authors with evidence.
Mr Martin said the report had vindicated Ireland's response to the allegations made by Israel that 12 UNRWA staff had taken part in the Hamas attacks of 7 October.
He said: "We were very clear from the word go that you could not replace or undermine UNRWA’s role in terms of giving vital aid, teaching, education.
"Half a million children in Gaza have been without education, and the only credible organisation that can deliver education is UNRWA.
"We took an opposite view to most countries, we actually increased our aid at that time, and I'm hoping now as a result of the publication of this report that some countries who have paused their support will now allow their support."
Mr Martin said Israel had wanted to undermine UNRWA because of its link to the return of Palestinian refugees following the Arab-Israeli War in 1948.
"UNRWA reflects the principle of the right of return of Palestinians in the event of a two-state solution.
"So, if you undermine UNRWA and remove UNRWA you essentially remove the right to return," he told reporters.
At the Rafah Crossing, the Tánaiste met officials working for the Egyptian Red Crescent and UNRWA to hear first hand about the challenges of getting humanitarian aid into Gaza.
Mr Martin is also due to meet injured patients at Al Airish Hospital.
On arrival at Cairo Airport last night, Mr Martin said Ireland had contributed €56 million in aid to the Palestinians since the start of the Gaza war, compared to the normal annual contribution of around €15 million.
The Tánaiste said the political leg of his visit to the Middle East was linked to Ireland’s intention, with a group of other EU and European states, to recognise Palestinian statehood.
He said that Egypt and Jordan, which he will travel on to after the Rafah visit, were central to both ceasefire talks and a broader regional peace effort.
While the recognition issue had previously been linked to the re-launch of the Arab Peace Initiative, which Egypt and Jordan have been co-sponsoring, as well as a ceasefire in Gaza, Mr Martin said a "third dimension" to recognition could be the vote in the UN General Assembly in early May on admitting Palestine to the United Nations.
The Tánaiste said that the vote could "underpin" a move by a number of EU member states, including Spain and Ireland, to recognise the State of Palestine.
However, he did not envisage such recognition happening before or on the date of the vote.
It is understood the timing is a sensitive one for a number of member states, given that the United Nations admitted the new state of Israel on 11 May 1949.
Following his visit to Rafah and the Humanitarian Hub at Al Airish, the Tánaiste's delegation will fly to Amman.
Mr Martin will meet the Jordanian Foreign Minister Ayman Safadi.
