Leading electrical and DIY retailers may be losing an estimated£8 billion in sales because of badly trained staff and poor stock availability.
Customers complained of rudeness and misinformation and, in some cases, branded staff 'clueless', 'stupid' and 'ignorant', a survey shows.
As a result of poor service and product information, 38 per cent of people said they failed to make a purchase they otherwise would have made.
The damning research, commissioned by retail solutions firms Blue Martini and Conchango, and carried out by Birmingham Business School, revealed 43 per cent thought overall service was 'just about acceptable' or worse.
One mystery shopper told how his visit to 'a well-known superstore' was held up while a pair of sales assistants finished kissing each other.
'We have uncovered quite staggering ignorance, indifference and efficiency in the customer-facing sales process,' said Blue Martini UK marketing manager Tania Andrews. She said many retailers are faced with the task of ensuring staff are able to give customers the necessary advice against a background of high staff turnover.
Respondents said Marks & Spencer, John Lewis and Sainsbury's had reputable levels of service, while those in home entertainment, white goods, computing and DIY were poor.
'Service will vary across the (electricals) sector as a whole. However, there is massive amount of investment in service at the moment,' said a Dixons Group spokesman.
He said Currys, for example, had already reaped the benefits of restructuring store teams last year, which ensured more people were available to serve customers. The spokesman also noted that the retailer could not speak 'on behalf of the entire sector'.
A B&Q spokeswoman said: 'We have experts in store, we do demonstrations and we focus on customer service - the warehouses are well staffed.'
Last year, service at B&Q was criticised in the press after comments made by then chief executive Bill Whiting. However, the spokeswoman said his comments were taken out of context.
'Bill's point was that if you ever think you're perfect, you're not - you can always improve,' she insisted. However, she conceded: 'Expectations are far higher in our sector than in others, such as food.'
PULLING THE PLUG ON SERVICE
Key causes of customer frustration
Lack of responsiveness: waiting for help
Limited product knowledge, understanding or weak explanations
Unreliable or inaccurate advice
Lack of empathy: staff not applying their knowledge to situation
Lack of assurance: incompetence, attitude, lack of credibility
Not being able to get the products they want (poor range, out of stock, having to order, having to wait)
Discrepancy between expected and delivered service
Retailers need to look urgently at the following areas
Service inconsistent because of dependence on people knowledge
Service inconsistent across channels
Consistency needed: same answers to questions from all staff
Provide greater empathy with shopper needs: ability to answer FAQs
For those that avoid staff contact, provide self-service in-store kiosks
Up-to-date information needed across all channels
Source: Blue Martini.