The union south of the Border has pointed out that while farm-gate prices have dropped by nearly one- quarter, and wholesale prices for UK legs of lamb are down by 17%, prices in the shops for UK product have only fallen by 2% in the same time period.
According to the NFU, the issue is not confined to UK lamb.
Figures show the wholesale price of New Zealand lamb has dropped by 23% (year on year), and yet the retail price for consumers has only come down 12% in the same period.
NFU livestock board chairman Charles Sercombe has highlighted the current farm-gate price for UK lamb is not viable in a period where sheep farmers have seen their costs rise.
He is also concerned the price of UK product on the shelves has not fallen by anywhere near the same amount as the farm-gate price.
Mr Sercombe said: "Currently farmers are suffering, and consumers aren't benefiting, so just who is reaping the rewards of the 'Great Lamb Robbery'?"
Meanwhile, the National Sheep Association Scottish region has expressed similar concerns over low prices north of the Border.
Its development officer, George Milne, said: "In the short-term it would be most beneficial to see some form of immediate action from the Scottish Government to provide QMS (Quality Meat Scotland) with short-term emergency support to undertake additional promotion to encourage the consumption of Scotch lamb and clear the numbers that have built up on farm following the exceptionally wet weather conditions."
LAWRIE & Symington sold 16 prime heifers in Lanark on Monday to a top of 239p per kg and an average of 221.2p (+16.2p on the week), while eight prime, beef- bred bullocks peaked at 227p and levelled at 209.7p (+5p),
Fifteen prime B&W bullocks averaged 172.6p (-1.4p).
In the rough ring, 44 beef cows averaged 125p, while 50 dairy cows levelled at 113p. Sixteen OTM cattle averaged 129p and three bulls levelled at 142p.
There were also 3081 prime hoggs that sold to £93 per head and 214.6p per kg to average 151.8p (-16.5p).
The 882 cast sheep forward saw ewes sell to £108.50 for Texels and £53.50 for Blackfaces to average £49.59 overall (-£1.38).
At the firm's fortnightly sale of dairy cattle the 13 head forward sold to £2220 for a Holstein heifer and averaged £1621 (-£110 on the previous sale).
Craig Wilson sold 1632 prime hoggs at Ayr on Monday to a top of £87 and 190.5p to average 146.4p (-5.9p).
There were also 531 cast sheep forward with Texel ewes sharper on the week, while Blackface and Mule ewes met a similar trade.
Rams sold to £130 for a pen of Texels, while ewes peaked at £139 for Texels and £48 for Blackfaces.