The timing of Prince William’s unprecedented intervention relating to the war in Gaza has raised questions about the involvement of the UK Foreign Office, and whether the royal statement was encouraged or even engineered to increase pressure on Israel.

On Tuesday, the Prince of Wales issued a statement saying “too many have been killed” in the conflict, and “I, like so many others, want to see an end to the fighting as soon as possible”.

It was a rare and bold royal foray into the complex world of international diplomacy and the long, painful history on both sides of the Israeli-Palestinian conflict.

The statement landed as the UK government has become more critical of the war ahead of Israel’s stated plan to launch a military offensive in Rafah, the town in the south of Gaza where about 1.4 million displaced Palestinians are sheltering. International pressure on the Israeli government to halt the bloodshed is mounting. Meanwhile, the Labour leadership is facing another potential rebellion among its MPs over the question of a ceasefire.

Prince William’s statement was issued before his visit to the British Red Cross in London to discuss the devastating humanitarian crisis in Gaza. The heir to the throne said: “There is a desperate need for increased humanitarian support to Gaza. It’s critical that aid gets in and hostages are released.”

The prince had thought “long and hard” before making his intervention, royal sources are reported to have said, but decided the extent of human suffering in Gaza compelled him to speak out.

The statement was issued with the knowledge of the Foreign, Commonwealth and Development Office (FCDO) and No 10 said the UK government welcomed the intervention. A spokesperson for the prime minister said the statement was “consistent with the government position … It is important that we speak [with] one voice as a nation”.

Some commentators speculated that the FCDO may have been rather more proactive than suggested. Ed Balls, the former shadow-chancellor turned broadcaster, raised the possibility on ITV’s Good Morning Britain that Lord Cameron, the foreign secretary, may have initiated the royal intervention.

Admitting he had no evidence to support his suggestion, Balls said: “If you’re thinking of intervention, this is the week to do it, help [the government] to ratchet up the pressure on Israel, now’s the time.”

Israel’s response to William’s statement was careful. Eylon Levy, a government spokesperson, said: “Israelis of course want to see an end to the fighting as soon as possible, and that will be possible once the 134 hostages are released and once the Hamas terror army threatening to repeat the October 7 atrocities is dismantled.

“We appreciate the Prince of Wales’s call for Hamas to free the hostages. We also recall with gratitude his statement from October 11 condemning Hamas’s terror attacks and reaffirming Israel’s right of self-defence against them.”

The Daily Telegraph reported that Israeli officials had been caught off-guard by the statement, but added: “It is understood that they consider [it] to be naive. They are dismayed, but it is thought they decided not to go further in criticising him publicly because they did not want to enter into a row with the future king.”

In the UK, Ephraim Mirvis, the chief rabbi, welcomed the prince’s “words of compassion”, and referenced a visit by William to Israel and the West Bank in 2018, saying he had since “shown a deep concern for the wellbeing of all those affected by the conflict in the Middle East”.

There was no such welcome for the statement from rightwing politicians. The Conservative peer Stewart Jackson said the intervention was “ill-timed and ill-judged”. The Tory MP Andrew Percy said: “The underlying principle of our constitutional monarchy is that members of the royal family do not engage in contentious political issues of the day on which there are divergent and strongly held beliefs in this country.”

Nigel Farage, the former Ukip leader, said it was a “step too far” for the country’s future king, and suggested he stick to presenting the Baftas.

The prince’s intervention was dismissed by Jonathan Purcell, of the UK-based International Centre of Justice for Palestinians. “We shouldn’t have to rely on royals to opine on the UK’s diplomatic response to Israel’s war on Gaza, while our elected officials quibble over phrasing, having dragged their heels for months in calling for an immediate ceasefire.

“The focus should not be on the musings of royals, but on the elected officials who vote against the motion [calling for an immediate ceasefire] or abstain, despite the British public’s overwhelming support for an immediate ceasefire.”

Ben Jamal, of the Palestine Solidarity Campaign, said: “It’s good that Prince William has spoken up. All decent people should be concerned at the level of killing in Gaza. But the reality of course is that the genocide Israel has unleashed on the Palestinians in Gaza is not going to end until Israel is held accountable for it by the international community, and serious pressure is applied on it to agree to a ceasefire.”

In 2018, Prince William became the first member of the royal family to visit the occupied West Bank. He toured a health centre and a school, both run by the United Nations Relief and Works Agency in a refugee camp, and told a gathering of Palestinian dignitaries: “You have not been forgotten.”

On Tuesday, the prince told British Red Cross executives in London that the visit had made a “lasting impression” on him and he has since followed the region closely. He said: “I’m always keeping an eye on what’s going on.”

William will also visit a synagogue this week to hear from young people from different communities who advocate against antisemitism.