An institute measuring customer satisfaction across UK businesses has warned the more difficult retail environment will make customer service more important in the coming years.

Amazon retained its place as the top organisation for customer satisfaction in the UK in the UK Customer Satisfaction Index, published by the Institute of Customer Service.

Meanwhile Iceland beat Aldi and Waitrose to be named the highest performing food retailer for the first time – the only food retailer to make it into the top 10 after climbing 26 places in the last six months.

The top spot when to US tech giant Amazon for the sixth consecutive time in the biannual survey with a score if 86.7 points out of 100, just ahead of John Lewis on 86.5 and Next and Yorkshire Bank, both on 86.1.

The banking sector performed better than ever before, reaching a score of 80.4 – above the overall average of 77.9 – with four financial institutions in the top 10 including Yorkshire Bank and Nationwide. Norwich-based insurer Aviva came in at number 22.

However, the index showed a slight fall over overall customer satisfaction after a peak in 2012/13.

The index rates customer satisfaction across 13 sectors based on the views of 10,000 consumers. More than 30 different customer measures are surveyed, such as staff professionalism, the quality and efficiency of the service, trust and transparency, the actual customer experience and complaint handling.

Jo Causon, chief executive of the Institute for Customer Service, warned of a 'stagnation' in customer service levels.

'This comes at a time when, just nine months from Brexit, we need more than ever before to show that Britain is a great place to do business with and in,' she said.

'Alongside tangible financial measures, trust, reputation and recommendation are crucial benefits of a deliberate and consistent focus on achieving high levels of customer satisfaction.'

The top 50 organisations in the July 2018 index are:

1 Amazon.co.uk

2 John Lewis Retail

3 = Next Retail, Yorkshire Bank

5 = first direct, Nationwide Building Society

7 Tesco Mobile

8 = M&S Bank, Wilko Retail

10 Iceland

11 Netflix

12 Specsavers

13 Pets at Home

14 = Greggs, Superdrug, Argos

17 = Trivago, Waitrose Retail

19 Nationwide Insurance

20 = Green Flag Services, Jet2holidays.com

22 Aviva

23 = Aldi, M&S (food)

25 = Jet2, LV=

27 Halfords autocentre

28 = eBay, Premier Inn

30 SAGA Insurance

31 Santander

32 M&S

33 = Holland & Barrett, Honda, Kia

36 Caffe Nero

37 = Brittany Ferries, Jaguar

39 = Apple, booking.com, Co-op Insurance, Mini, TSB

44 = giffgaff, More Than, Primark

47 Halifax

48 = Lidl, Subway, Toby Carvery