Iran has called Israeli Prime Minister Benjamin Netanyahu a "liar" after he accused the country of deceiving the world about its nuclear intentions.
Mr Netanyahu produced what he said were copies of Iranian files detailing a project to build nuclear weapons, which was reportedly mothballed 15 years ago.
Iran said it had never sought to build a bomb when it signed an international deal to curb nuclear activity in 2015.
US President Donald Trump has threatened to pull out of the deal.
American allies like the UK and France have called for the agreement to be maintained, arguing that Iran has abided by it, steadily reducing its capacity to produce weapons-grade uranium.
Hostility between Israel and Iran, already bitter enemies, has grown as Iran builds up its military in Syria, on Israel's doorstep.
What did Iran say?
Foreign ministry spokesman Bahram Ghasemi described Mr Netanyahu as an "infamous liar who has had nothing to offer except lies and deceits".
His accusations, he continued, were "worn-out, useless and shameful".
Foreign Minister Javad Zarif said the documents produced by Israel were a rehash of old allegations already dealt with by the International Atomic Energy Agency (IAEA), the UN's nuclear watchdog.
What is the thrust of Israel's case?
Israel says that Iran is not a reliable partner and the 2015 agreement was reached in bad faith.
Speaking after Mr Netanyahu's presentation of the alleged secret Iranian files, Mark Regev, the Israeli ambassador to London, said the Iranian government had deliberately concealed its military nuclear programme.
"It appears we've caught them red-handed lying about what is ultimately a crucial element in the deal, one which is a prerequisite for future implementation of that very deal," he said.
Not only did Mr Netanyahu give alleged details of Project Amad, the alleged Iranian nuclear weapons programme reportedly mothballed in 2003, but he said the project had continued at the Iranian defence ministry.
He quoted the head of the alleged programme as saying "special activities" would continue "under the title of scientific know-how developments".
Such work continued this year, Mr Netanyahu said, without giving evidence.