U.K. business confidence sank to a four-and-a-half-year low in the days after Britons voted to leave the European Union, adding to evidence that the decision is blighting growth.

With investors anxiously awaiting data on the Brexit's consequences, the gauge compounds signs that the referendum has hindered an economy that was already losing momentum. Even reports covering the period before the vote are showing signs of fragility, with Halifax saying house-price growth cooled in June. GfK is due to publish a one-off survey Friday that will assess consumer attitudes in the immediate aftermath.

The National Institute of Economic and Social Research said Thursday that its growth estimate for June is "one of intensifying contraction across the board." While it predicts growth of 0.6 percent in the second quarter, that's boosted by a strong figure for April. Once that drops out of the calculation, the institute expects "a quick deterioration."