More than 200 staff members of EU institutions and agencies have signed a letter expressing “growing concern” over the union’s response to the humanitarian crisis in Gaza, arguing that it runs contrary to its core values and aim of promoting peace.

The letter, signed by 211 people in their personal capacity as citizens and addressed to the EU’s top three officials, begins by condemning the 7 October attacks “in the strongest terms”.

Citing the January ruling by the international court of justice that suggested a credible risk to Palestinians under the genocide convention, the letter warns that the EU’s “continued apathy to the plight of Palestinians” risks normalising a world order where the sheer use of force, rather than a rule-based system, determines state security, territorial integrity and political independence.

“It was precisely to avert such a grim world order that our grandparents, witnesses of the horrors of World War II, created Europe,” the letter reads. “To stand idly by in the face of such an erosion of the international rule of law would mean failing the European project as envisaged by them. This cannot happen in our name.”

The letter, shared exclusively with the Guardian, was written by a small group of staffers, said Zeno Benetti, one of the organisers.

“We couldn’t believe that our leaders who were so vocal about human rights and who described Europe as the beacon of human rights were suddenly so silent about the crisis unfolding in Gaza,” he said. “It’s like suddenly we were asked to turn a blind eye on our values and on the values that we were allegedly working for. And for us, this was not acceptable.”

Organisers had hoped to reach 100 signatures – a figure that was swiftly surpassed as word of the letter spread. A version of the letter made public on Friday does not include the names of those who signed as they were promised confidentiality by the organisers.

The letter highlights the many NGOs that have repeatedly called for a ceasefire, adding: “The EU’s inability to respond to these increasingly desperate calls is in clear contradiction with the values that the EU stands for and that we stand for.”

It urges the EU to officially call for an immediate and permanent ceasefire, adding this to a list of requests that include officially calling for the release of all hostages and to ensure that member states halt direct and indirect arms exports to Israel.

Benetti emphasised that the initiative was not meant to be pro-Palestinian, nor was it aimed at taking a partisan stance on the conflict. “Rather, we signed because we think that what’s happening is jeopardising principles of international law that we deem important and that we take for granted,” he said.

The letter is expected to be delivered on Friday to Ursula von der Leyen, the president of the European Commission, as well as Roberta Metsola, the president of the European parliament, and Charles Michel, who heads the European Council.

It comes weeks after more than 100 EU staffers marched through Brussels to protest against Israel’s war in Gaza. “We’re coming together in a peaceful assembly, to stand up for those rights, principles and values that the European institutions are built on,” the European Commission staff member Manus Carlisle told Reuters at the time.

Ashifa Kassam European Community affairs correspondent