This is the first time that Shell, commonly regarded as a conservatively managed group, has been considered as a possible predator for Lasmo. Although many believe that a bid would be against Shell's management style, there is a growing belief that it may be considering making a move.
The company declined to comment.
It is understood that Shell is preparing a knock-out punch against Lasmo, which has long been regarded as a sitting duck for takeover.
Other potential bidders include British Gas and Elf, the French group.
Lasmo's shares have slumped by 40 per cent since it completed a pounds 1bn takeover of Ultramar, the oil refiner, in January.
The shares are the worst performers among Britain's top 100 blue chips and fell 8p to close at 117p on Friday.
Later this week, it is expected to report a sharp fall in interim profits. Analysts believe the net figure could slump from pounds 30m to pounds 10m for the half-year to 30 June. There are also fears that it may be forced to cut the 2.3p dividend.
However, it is one of the world's biggest oil and gas independents, with total commercial reserves of more than 1.3 billion barrels of oil and daily production of about 200,000 barrels.
One of the largest operators in the North Sea, it has a substantial interest in the Indonesian gas market.
Although Shell has cultivated a low corporate profile, it has a successful track record as a predator. Its Australian arm is involved in a hostile dollars 30m takeover of Austen & Butta, an Australian coal mining company of which it already owns 49.5 per cent.
Three years ago, Shell shocked the US oil industry with an audacious dollars 3.7bn takeover bid for Belridge Oil. The company won control by offering twice the amount put up by Texaco and Mobil.Reuse content