The government has announced a 3.8% increase in the wage, which will result in the adult rate rising from £5.52 to £5.73 from October 1, 2008.
The increase is well above the 2.2% inflation rate and more than many public sector increases which were kept below 2.5%.
The rate for 18- to 21-year-olds will go up in October from £4.60 to £4.77, while the 16- to 17-year-old rate will rise from £3.40 to £3.53. The latest increase means that the wage has risen by 59% since its introduction in 1999 - more than double the rate predicted.
Retailer Vikram Karavadra, whose family owns two Londis stores in Northampton, said the increases needed to be more sensible. "If it rose each year in line with inflation it would be fairer," he told Convenience Store. "When the minimum rate increases there is also a knock-on effect for all our other wage levels. I understand things are getting more expensive, but we're having to cope with increased costs ourselves."
David Smith from Smith's Corner Store, Grimoldby, Lincolnshire, agreed: "The problem is that the cost of everything for us as retailers is increasing. We've also got to cope with things like rising fuel costs, increases to holiday entitlement and possible compulsory pension payments."
The Association of Convenience Stores (ACS) and the British Retail Consortium (BRC) also expressed disappointment at the increase.
ACS chief executive James Lowman described it as "unacceptable" and said: "If the majority of workers in the country are receiving inflation-linked rises of about the 2% mark then why should small businesses such as convenience stores that already have to deal with the burden of increasing regulation have to foot the bill?
"Why are we expected to afford pay increases greater than those the government is prepared to pay itself?"