(Reuters) - UK shares were lower on Monday as online fashion store ASOS' profit warning dragged retailers lower, reinforcing woes about slow sales during the busy holiday season amid continued caution about the UK's divorce from the European Union.
The UK blue-chip bourse <.FTSE> was down 0.2 percent at 0900 GMT, while the mid-cap index <.FTMC> was down 0.2 percent.
The alert from AIM-listed ASOS set the tone for the market after the company lowered its full-year margin and sales growth forecasts as November trade fell short of expectations.
The shares plunged nearly 37 percent to its lowest in three years, wiping 1.3 billion pounds of the company's market capitalisation.
Among big fallers on the main index were high street retailers Next <NXT.L> and Marks & Spencer <MKS.L>, down 8.3 percent and 4.4 percent respectively.
ASOS rival Boohoo <BOOH.L> fell as much as 18 percent at the open, before recouping some losses after it reported record Black Friday sales. It was last down 9.8 percent.
High street chains were also the biggest drags on the mid-cap index, with JD Sports Fashion <JD.L> dropping nearly 4 percent and Sports Direct <SPD.L> losing 3 percent.
Financial heavyweights Prudential <PRU.L> and Barclays <BARC.L> each gave up roughly 1 percent in early trade.
Oil and related stocks also fell as crude prices remained under pressure amid weaker growth in major economies and concerns about oversupply.
Shares in energy provider SSE <SSE.L> gave up 1.3 percent after it scrapped a deal with Innogy SE <IGY.DE> for a tie-up that would have created UK's second biggest retail power provider as the companies failed to agree on revised terms.
(Reporting by Muvija M in Bengaluru; editing by Josephine Mason)