Investigating customer experiences with the UK's 100 biggest brands, Which? asked participants to rate firms in three customer service categories - knowledge, staff attitude and dealing with issues.
Bottom of the pile was Michael O'Leary's low-cost airline, which received just two out of a possible five stars in each category.
At the other end of the scale, cosmetics company Lush topped the table, achieving a five-star rating in all three categories and a customer satisfaction rating of 88 per cent. Lakeland was just behind in second place, while John Lewis, First Direct, RAC, Waitrose and Amazon were also found to be keeping their customer's happy.
Yet of the 3,331 people polled, 86 per cent said they would leave a brand that treated them badly, and four out of ten would be happy to pay more for quality customer service.
Richard Dilks, policy adviser at Which?, told the Daily Mail: "Outstanding service can leave you feeling positive, valued and likely to want to repeat the experience.
"Terrible customer service can leave you feeling stressed, frustrated, angry and, in many cases, never wanting that experience again."
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