According to the
UK Customer Satisfaction Index, the online retailer provides the best customer service in the UK, based on the views of 10,000 respondents.
The company has moved up from second place last year and is closely followed by Utility Warehouse, and First Direct.
Also in the top ten were Specsavers, New Look and SAGA Insurance, all of whom posted impressive increases of more than three points over year.
Retail non-food remained the sector with the highest satisfaction score, but utilities improved most, gaining 1.9 points on last year, closely followed by insurance (1.6) and retail food (1.5).
Banks and building societies fell by 0.4 points despite improving significantly since the banking crisis.
The index showed the first significant boost in customer satisfaction since 2012, a rise of 0.8 points to 77 (out of 100) but was still some way off the 2013 peak of 78.2.
According to the research, competence of staff was considered the most important element for customers in 2015, having been ranked only eleventh in 2010.
Staff ‘doing what they say they will do’ and competence on the phone were the next most important priorities for customers.
Helpfulness of staff, in person, rose from 21st to fourth in the rankings while friendliness of staff and ease of doing business also rose on the index of customer priorities.
Commenting on the findings, Jo Causon, CEO of The Institute of Customer Service, said: “Core ingredients of excellent customer service - employee competence, attitudes and behaviour - have become even more significant differentiators.
“Mass marketing or a ‘one size fits all’ customer experience is delivering diminishing returns and diluting valuable customer relationships.
“The insight we have gathered from this UKCSI identifies the components of excellent service and where strategic and operational effort should be focused to make further improvements.
“While the multi-channel environment demanded by customers has the potential to offer a faster more flexible service, it can also exacerbate problems if not done correctly.
“Challenger brands, often unencumbered by legacy systems and processes are gaining on their larger competitors by offering straightforward, personal, seamless and quick service experience.
“This is reshaping the competitive environment around customer service and removing barriers to entry to create a real opportunity for smaller organisations to succeed against larger rivals.”