By Khushi Singh and Bansari Mayur Kamdar
(Reuters) -Britain's main stock indexes fell on Wednesday with mid-cap stocks nearing one-year lows as Spirent Communications (LON:SPT) sank after a profit warning, while weak energy and mining shares dragged down the commodity-heavy FTSE 100 for the third straight day.
The benchmark FTSE 100 index shed 0.8% and the domestically-focused FTSE 250 index closed 1.1% lower.
The energy sector fell 2.5%, tracking weak crude prices as demand fears stemming from macroeconomic headwinds offset pledges by Saudi Arabia and Russia to continue crude output cuts to the end of 2023.
Concerns about global growth also weighed on UK equities after bond yields rallied on bets that interest rates will have to stay high to dampen inflation.
Heavyweight industrial metal miners lost 1.8% as copper prices fell to their lowest in more than four months.
Tesco (LON:TSCO) gained 4.3% after the country's biggest retailer raised its annual profit forecast and signalled that food inflation would continue to decline.
"Tesco's progress has been remarkable, and largely possible because of its enormous scale," said Sophie Lund-Yates, lead equity analyst at Hargreaves Lansdown (LON:HRGV).
"The real test will be Christmas, where consumers will want to put on as much of a feast as possible, but where wallets may not allow it. We could be faced with a race to the bottom on festive pricing, which could spell trouble for margins."
Shares of Spirent Communications fell 31.3% to lead declines on the midcap index after the telecoms testing services provider warned of lower annual profit.
Fashion retailer Superdry jumped 17.8% on news that it would sell its intellectual property assets in South Asia to Reliance Retail.