By Olivia Le Poidevin

GENEVA (Reuters) -A Swiss-based NGO has asked authorities to investigate the activities of the Gaza Humanitarian Foundation (GHF), a U.S.-backed organisation that plans to oversee a new model of aid distribution in the Palestinian enclave that the UN opposes.

The United Nations has said the GHF's aid plan is not impartial or neutral, and forces further displacement and exposes thousands of people to harm, and that it will not be involved.

The GHF, which has said it hopes to start work in Gaza by the end of May, told Reuters it "strictly adheres" to humanitarian principles, and that it would not support any form of forced relocation of civilians.

Israel has allowed limited aid deliveries to resume this week after having stopped all aid deliveries to Gaza on March 2.

TRIAL International, a Switzerland-based NGO, on Friday said it had filed two legal submissions asking Swiss authorities to investigate GHF, which is registered in Geneva.

A May 20 submission to the Swiss Federal Supervisory Authority for Foundations, and one on May 21 to the Swiss Federal Department of Foreign Affairs (FDFA), requested an investigation into whether the GHF complies with Swiss law and international humanitarian law.

The Swiss FDFA and the Federal Department of Home Affairs were not immediately available for comment.

"We're asking Switzerland to exercise their own obligation under the Geneva Conventions to respect international humanitarian law...there are very grave issues at stake," Philip Grant the Executive Director of TRIAL International told Reuters.

TRIAL International said it asked the Swiss FDFA to explain if the GHF had submitted a declaration, in accordance with Swiss law, to use private security companies to distribute aid, and if it had been approved by Swiss authorities.

The GHF told Reuters that though using private security firms represents a change from prior aid delivery frameworks, it would ensure aid is not diverted to Hamas or criminal organizations.

(Reporting by Olivia Le Poidevin; additional reporting by Emma Farge and Michelle Nichols; Editing by Conor Humphries)