Hundreds of world leaders and politicians will descend on Istanbul on Monday in a nominal attempt to reform the global humanitarian system, despite criticism that their summit is a photo-opportunity that will achieve little.

Representatives of 175 countries, including 57 heads of states or governments, will attend the world humanitarian summit, as the outgoing UN secretary general, Ban Ki-moon, attempts to restructure the way the world responds to humanitarian crises.

Angela Merkel is the highest-profile western leader due to attend, while Britain will be represented by development secretary Justine Greening. About 6,000 senior aid workers will also participate in debates and panels at the two-day event.

With more people – about 125 million – in need of humanitarian assistance than ever, aid groups increasingly under-resourced, and international law under growing threat, Ban wants the international community to agree to new global humanitarian standards.

The key commitments to which he hopes leaders will agree include better structuring of aid; more funding for local groups; greater respect for the rules of war; better planning for disaster situations and climate change; and wider sharing of refugee populations.

Hailing the prospects of the summit, Herve Verhoosel, the summit’s spokesman, said: “It’s the first time in 70 years of UN history that a summit has been organised to talk about humanitarian issues. Today we’re living in the worst humanitarian situation since world war two – we have 125 million people in need of humanitarian support in the world. Can we cope with that situation working the same way we do today, or do we need to change it? That’s why the secretary general has called this conference.”

There is nevertheless mounting criticism of the summit from aid and rights workers, with Médecins Sans Frontières calling it a “fig-leaf” for international failures, and Oxfam describing it as an “expensive talking shop”. A columnist in Foreign Policy, an American magazine, wondered if it “could do more harm than good”.

MSF has even pulled out of the conference, saying it no longer believes that the assembled leaders have any genuine desire to make binding commitments. Speaking to the Guardian, MSF’s UK director, Vickie Hawkins, said it was unlikely that the same countries who are currently shirking their obligations to refugees would turn over a new leaf next week.

“The contradiction became too much for us,” said Hawkins. “We didn’t have any confidence that anything different will come out of the conference. There’s a lot of good intentions, but also empty rhetoric. And we felt we needed more than that, given the current disregard for international law.”

Hawkins also warned that the summit’s goals had become too grand, and also too political for independent aid groups like hers to agree to. “For us, the word ‘humanitarian’ has dropped out of the humanitarian summit,” Hawkins said. “It has become a summit about a much broader and longer-term political agenda, rather than being about core humanitarian assistance.”

Oxfam GB’s chief executive, Mark Goldring, said: “This summit needs to be more than an expensive talking shop by tackling the repeated failure of governments to resolve conflicts and end the culture of impunity in which civilians are killed without consequence.

Goldring added: “Rich nations cannot wash their hands of the suffering for which they are partly responsible and [must] do more to take in their fair share of the world’s most vulnerable people. Recent moves such as the EU-Turkey deal and the plans to outsource EU border controls to African countries with dubious human rights records set a dangerous precedent, horse trading the rights of refugees in order to keep them from our doorstep and shirking responsibility for their welfare.

“Last week, the Kenyan government pointed to the example of European countries turning away Syrian refugees when it announced the closure of the Dadaab refugee camp.”

Verhoosel said he was disappointed by the criticism, arguing that the UN and its members had to start somewhere, and that this week’s gathering could be that starting point.

“We need to try to do what we can during the summit,” said Verhoosel, questioning how critics could pre-empt the outcome of an event that has not yet happened. “Maybe they have a crystal ball?”