LONDON (Reuters) - Britain's decision to allow the export of F-35 fighter jet components to Israel, despite accepting they could be used in breach of international humanitarian law in Gaza, was unlawful, a Palestinian rights group told London's High Court on Tuesday.

Al-Haq, a group based in the Israeli-occupied West Bank, is taking legal action against Britain's Department for Business and Trade over its decision to exempt F-35 parts when it suspended some arms export licences last year.

The United Kingdom had assessed that Israel was not committed to complying with international humanitarian law, in relation to humanitarian access and the treatment of detainees, as the basis for its decision in September.

But, after the Ministry of Defence said suspending licences for F-35 parts would have an impact on international security and "undermine U.S. confidence in the UK and NATO", Britain decided to "carve out" F-35 licences.

Al-Haq, which documents alleged rights violations by Israel and the Palestinian Authority, the Palestinians' self-rule body in the West Bank, argues that the ministry's decision was unlawful as it was in breach of Britain's obligations under international law, including the Geneva Convention.

The group's lawyer, Raza Husain, said its case at the High Court was being heard "against a backdrop of human calamity unfolding in Gaza", since Israel responded to the October 7, 2023 Hamas attacks with a devastating military campaign.

Nearly 53,000 Palestinians have been killed, according to Hamas-run Gaza health authorities.

Husain said the vast majority of Al-Haq's case did not require the High Court to rule on "the lawfulness or otherwise" of Israel's actions in Gaza, but whether British ministers had misunderstood the law when it decided on the F-35 carve-out.

The British government, however, argues ministers were entitled to take "exceptional measures" to not suspend F-35 licences to avoid the potential impact on international peace and security.

Its lawyer, James Eadie, said in court filings that the decision was "consistent with the UK's domestic and international legal obligations".

Last year, a coalition of groups, including Al-Haq, asked a Dutch court to stop the Netherlands exporting weaponry to Israel and trading with Israeli settlements in occupied Palestinian territories.

Israel says it takes care to avoid harming civilians and denies committing abuses or war crimes in Gaza.

In March Israel ended a January ceasefire deal with Hamas, after the two sides could not agree on terms for extending it, and renewed its military operations.

(Reporting by Sam Tobin; editing by Mark Heinrich)