The annual Billetts Trade Promotions Survey polled executives at 83 leading fmcg suppliers on the quality of promotional execution at leading supermarkets.
While Waitrose typically ran half as many promotions as its big four rivals, suppliers said its execution was more appropriate and effective.
"Manufacturers are really rewarding Waitrose for its more focused approach," said Billetts director Ian Fermor. "There's a definite sense, with some retailers, of indiscriminate and often inappropriate activity."
With promotional spend at an all-time high, 43% of suppliers made more than 40% of their sales on promotion, almost treble the 16% of five years ago. And 12% of suppliers believe they now spend "far too much" on promotions, up sixfold on the 2% in 2005.
The survey found that, of the big four, Morrisons remains the benchmark for promotional execution. The hallmarks of a good promotion were "relevant products, targeted product choice, real value, simple communication", said group trading director Martyn Jones. "And availability is absolutely key."
But, speaking at The Grocer's Trade Promotion Conference on Tuesday, he agreed strategies were often poorly conceived and executed. He cited discounting 2-litre Pepsi and Coke . "All you end up doing is cannibalising volume, extending the promotional tail and diluting profitability."
And Sam Perkins, Tesco category director for household, called for "a new relationship" between retailers and suppliers to grow sales. "Profit is a challenge but not the biggest we face. What should unify us is that we don't have a way of growing sales together sustainably with our current dependence on promotions."
Tesco changes six million shelf-edge labels in store every third Wednesday as new promotions come in, Perkins estimated. "The complexity we're coping with is stifling our ability to think our way through this."
Asda, which came last in the survey, "has become a very confusing place to shop", believes Fermor. "With its obsession with round-pounds you can find two SKUs on a gondola end, one better than half price and the other at a 15% discount.
"The analysis we've done on Asda shows there's almost a breakdown in the price-volume relationship in some categories because consumers are becoming so confused about what the discount is."
Comply or die: how the major mults stack up on promotional execution
1st place: Waitrose
"Designed to entice new buyers to new categories; at the same time, do not devalue the categories"
2nd place: Morrisons
"By far the best with execution. You get what you pay for"
"Its promotion forecasting is also extremely accurate"
3rd place: Tesco
"Big improvement over last 18 months"
Better in-store support to clarify deals would improve performance"
4th place: Sainsbury's
"PoS execution best of big four but uplifts much lower"
"Recently JS has been appalling with in-store execution"
5th place: Asda
"Wine promotions well executed but getting a brand message across is a challenge"