TWO firefighting boats are standing by to deal with a possible catastrophe if escaping gas connects with a burning flare above a stricken North Sea oil platform and explodes.

The vessels were last night lying off Total's deserted Elgin rig with another boat carrying a remotely operated vehicle (ROV) which may have to carry out emergency repairs on the pipe thought to be carrying the gas.

The French oil giant announced the measures as it faced criticism of its apparent lack of transparency over the incident, which has led to the imposition of a three-mile air and five-mile sea exclusion zone around the area 150 miles off Aberdeen.

Unions had expressed concern before it emerged the flare could not be turned off remotely, amid fears changes to the prevailing wind direction may cause it to make contact with the gas and causing a blast.

Jake Molloy, from the RMT, said he thought it was "beyond comprehension" that the flare was still burning.

He added: "This is an unprecedented situation and we really are in the realms of the unknown but the urgent need now is to find a way of stopping the flow of gas."

Total admitted the flare, which is part of the platform's safety system used to aid the evacuation of its 238 personnel on Sunday, cannot be purged. It said the flare will eventually burn out and at present did not pose "an immediate risk".

In a statement, Total said: "The layout is designed to take into account the prevailing wind direction, ensuring that these winds are taking any gas from a potential leak in the wellhead area in the opposition direction to the flare.

"This is in fact exactly what is happening.

"The wind is forecast to remain in is current direction for the coming days. This is being reviewed on a constant basis and should this change any impact is being assessed. In parallel, we are investigating solutions to extinguish the flare if it does not burn out by itself."

Earlier, UK Energy Minister Charles Hendry suggested the flare could be turned off remotely.

There were also conflicting reports as to whether the flare would burn itself out in hours, days or longer.

It could take as long as six months to drill a relief well to stop the release of gas, according to Total.

A large sheen on the water is present near the platform, estimated to extend over 1.85 square miles and measuring between two and 20 tonnes in volume.

The company posted a statement about the incident on its emergency website yesterday afternoon, the first since Monday night.

Scottish Environment Secretary Richard Lochhead said: "Any gas leak on an evacuated offshore installation is, of course, deeply worrying.

"Therefore it's critical both Total and the UK Government ensure absolute transparency, with all information placed in the public domain.

"This should include not just details on the level of risk, but also how this is calculated."

RSPB Scotland's director Stuart Housden said: "We hope that, second to minimising risks to people, environmental considerations will be foremost in the mind of Total when considering their response to this situation.

"We urgently need to know exactly what environmental impacts the leaking substances could have."

Meanwhile, Total's share price has dropped by around 7% over the past two days.