UK retailer John Lewis said a possible no-deal Brexit could worsen already difficult trading conditions after first-half operating losses at the group's department stores widened and that the impact could be "significant". 

The partnership, which runs the department stores business and up-market supermarket Waitrose, reported a loss before its partner bonus, tax and one-off costs of £25.9m. 

John Lewis has said the main risk to the partnership from an unmanaged Brexit was a sharp fall in consumer confidence and the impact that would have on trading. 

"Should the UK leave the EU without a deal, we expect the effect to be significant and it will not be possible to mitigate that impact," said Charlie Mayfield, chairman of the John Lewis Partnership. 

"Brexit continues to weigh on consumer sentiment at a crucial time for the sector as we enter the peak trading period," he added. 

British Prime Minister Boris Johnson has pledged to take Britain out of the European Union with or without a deal on October 31, and has said he will not ask for a delay despite lawmakers voting that he seeks one to avoid a no-deal Brexit. 

At the same time, Britain's department store sector has been under intense pressure from weak demand and rising costs for several years. 

British Home Stores (BHS) went bust in 2016, House of Fraser was bought out of administration last year by Mike Ashley's Sports Direct, and Debenhams went into administration in April and is now owned by its lenders. 

For John Lewis, operating losses before exceptionals for its department store chain increased by £42.5m to £61.8m in the six months to July 27.

That contrasted with a rise in Waitrose's operating profit before exceptionals of £14.1m to £110.1m.