Inventories have swelled to the highest level on record as crude producers intensify the battle for market share, putting unprecedented strain on the world’s energy infrastructure. The International Energy Agency, the west’s oil forecaster, said stocks in developed countries had ballooned to almost 3bn barrels — the equivalent to more than a month’s supply of global oil consumption. Even though demand has been robust this year, crude inventories have continued to rise at more than 1m barrels a day, with storage tanks filling quickly and long lines of ships forming at key ports around the world. As a result oil prices, which have halved in the past 18 months, might fall even further to encourage refiners to process more crude and force more production offline, traders said. Brent crude, the global benchmark, fell to below $44 a barrel on Friday. “This massive cushion has inflated even as the global oil market adjusts to $50 [a barrel] oil,” the IEA said in its monthly report.