A HUGE oil tanker giving off a pungent pong was asked to leave Hamble's giant BP oil terminal to purge its tanks at sea.

BP staff noticed the offensive smell from gas identified as mercaptan sulphide as the Maltese-registered Isabella was being loaded with 16,500 barrels of crude oil from Wytch Farm yesterday.

People downwind of the nasty niff mistook it for a gas leak and rang British Gas and Transco.

But BP took immediate action to inform the environment Agency, local councils and British Gas about the situation as soon as they realised what was happening.

Isabella had previously unloaded high sulphur crude oil at Esso and had crossed Southampton Water to load up with low sulphur crude at BP.

A BP spokesman said: "It had been on the berth for two hours when we noticed that its tanks were giving off this smell.

"We immediately reduced the rate we were loading it to cut down on the emission.

"The wind was south-westerly, so most of this odour was carried down through Warsash and Fareham. We are extremely sorry if anyone was inconvenienced by what happened."

After realising that gas was still being emitted, Hamble terminal's marine superintendent Capt Peter Roberts stopped loading completely and then asked the ship to leave the berth.

It sailed at 9pm yesterday and was heading for the Nab Tower where it was due to purge its tanks with inert gas.

The BP spokesman said: "It will be back in a few days and we will then start loading at a very low pressure to see if there are any more emissions."

He added that mercaptan sulphide was a residue of high sulphur crude oil.

An Eastleigh Council environmental health spokesman confirmed that although highly odorous, the gas was not a danger to health at the level detected by smell.

Hamble Parish clerk Kate Cullen said she had not received any complaints from local residents about the nasty niff but had been informed about the situation by BP.