A protester has said Japanese Coast guards opened fire on his anti-whaling ship, but officials have denied the accusation.
Activists attacked the Japanese ship to try to stop whaling
Dan Bebawi, 28, from Nottingham, was on the Sea Shepherd vessel "Steve Irwin" on its mission to stop whale hunting.
He said the coastguard crew threw incendiary devices and fired live bullets onto the ship.
The Ministry of Foreign Affairs of Japan said it was trying to deter an attack but no lethal weapons were used.
Mr Bebawi told BBC Radio Nottingham that during the attack about two weeks ago, the coastguards threw incendiary devices and fired live bullets onto the ship.
"It was fairly frightening but we are prepared for the whaling fleet to use force against us. That is their decision but we will not back down," Mr Bebawi said.
He added that Captain Paul Watson was hit in the chest.
The Ministry of Foreign Affairs of Japan said the Sea Shepherd vessel had staged four waves of assault against the Nisshin Maru by throwing bottles of butyric acid on 7 March.
It said the officers threw seven "sound balls", which emit a loud noise, towards the ship, but no harm was done and no injury caused.
Mr Bebawi said: "We are here to intervene and stop the whaling. We have managed to halt them from whaling for five weeks.
"We will go as far as is needed without anyone causing any harm," he said.
He said they threw bottles of food additive that smells like rancid butter on the deck of the whaling ship.
Japan had planned to kill up to 900 minke whales and 50 fin whales during the expedition.
Tokyo said it carried out whaling for scientific research, but critics say the same data can be collected without killing the animals.