John Lewis, Britain's biggest department store, posted a 4.8% rise in sales to 777 million in the five weeks to Dec. 27, largely thanks to "Black Friday."During the week of Black Friday, the retailer had its biggest weeks of sales in its 150-year history, the Financial Times reports.In the US, Black Friday marks the day after Thanksgiving when retailers offer lower price deals. Amazon brought the day of heavy discounting over to Britain in 2010. However, it really took off this year.But John Lewis managing director Andy Street isn't sold on Black Friday promotions. He's concerned that the one-day event leads to a quick spike in sales that could eat into Christmas shopping."We've got to ask if it's right to concentrate trade so much in that one period,"Street told the BBC."I don't think we can put the genie back in the bottle ' I think absolutely those discounts, particularly those discounts in the electrical sector, are going to be a feature. But do we need to stoke that fire anymore' I personally hope not," Street said in an interview with the BBC's Kama Ahmed.Street also pointed out how some delivery businesses, such as Yodel, had difficulty fulfilling orders during the mass ordering rush.There's also the question of whether retailers need Black Friday to boost sales at all. Analysts "argue that purchases made during the Black Friday period would have happened anyway ' and probably at a higher price," the Financial Times writes.Despite concerns about how Black Friday might affect Christmas shopping behavior, John Lewis enjoyed a strong holiday period. "Customers did indeed turn to store for the final few days of shopping with sales particularly strong for our Oxford Street flagship and good performances from Exeter and Stratford City," the company said in a statement.Online sales were up 19% during the Christmas period compared with the previous year. The click & collect delivery service broke records, representing 56% of online sales.SEE ALSO:Tesco CEO Makes An Extraordinary Admission After Profits CollapseJoin the conversation about this story Click here to read full news..