Earlier this week, the company admitted to some further delays, but indicated that final preparations for oil production were going smoothly enough, though bad weather had caused some disruptions.

Offshore Journal has now learned that six production well trees are having to be removed from the seafloor for remedial work, including to valve actuation equipment.

There has also been talk of further subsea production manifold problems, following on from those which forced BP to lift the first sub-sea production centre several months ago for repairs. Depending on how severe this latest setback is, first commercial oil looks like being pushed back several weeks, perhaps months.

Compounding BP's latest difficulties has been the formation of hydrates (mix of frozen gas and water) and wax deposits in the network of subsea flowlines feeding oil to the production manifolds, though it is said that the riser system tying these to the production ship, Petrojarl Foinaven, is unaffected.

The culprit has been flows of super-cooled water flowing down from the Arctic at seabed level. Such flows can register -4C and lower and have long been known to fishermen as they are fast moving and deadly for fish such a cod.

Foinaven crude is already relatively cool and known to be waxy.

BP had hoped to bring Foinaven onstream more than a year ago. It was "officially" late by December and is now well over the original budget of some £55Omillion.

A spokesman for the company declined to ecomment when approached yesterday.