The 10 Opec members with output restrictions pumped 1.86 million bpd, or nine per cent, above Opec's official ceiling of 21.7 million bpd, according to the survey of industry officials, supply monitors and analysts.
The 10 countries pumped 23.56 million bpd in June, 340,000 bpd more than in June, the survey found. It was the worst quota compliance by the Opec in four years since it began a series of drastic supply cuts in 1998.
Iraq, which has no quota because of UN sanctions, pumped 1.71 million bpd in July, well below its capacity of almost three million as the UN's retroactive oil pricing policy deterred buyers.
Total Opec output stood at 25.27 million bpd, 370,000 bpd more than June. The largest hike came from Saudi Arabia, although estimates of production there varied widely from 7.53 to 7.75 million bpd.
Nigeria, which is facing a big fiscal deficit ahead of presidential elections next year, raised supply by 70,000 to 1.92 million bpd, the survey found.
The west African country shut down 300,000 bpd of Escravos crude oil for four days from July 21 because of a fire at an export terminal, but most of the affected loadings were replaced by alternative Nigerian crudes or from storage, dealers said.
Algeria also continued its steady upwards trend in oil production, fuelled by growing foreign investment. Both Algeria and Nigeria have called ©