U.K. retail prices continued rising in May, with inflationary pressures likely to increase before they ease, according to the latest report by the British Retail Consortium and NielsenIQ.

Retail prices rose by 2.8% in May, up from 2.7% in April, the report said, noting that they reached the highest rate of inflation since July 2011.

“With little sign that the cost burden on retailers will ease any time soon, they will be left with little room for maneuver, especially those whose supply chains are affected by lockdowns in China and the war in Ukraine,” Helen Dickinson, the British Retail Consortium’s chief executive, said.

Food inflation accelerated to 4.3% in May on a year-over-year basis, and up from 3.5% in the prior month, also reaching its highest inflation rate since April 2012, the report said. Fresh-food inflation accelerated in May to 4.5% from 3.5% in April, and ambient-food prices rose to 4% from 3.5% in the prior month.

Nonfood prices, on the other hand, decelerated to 2% in May from 2.2% in April, the report noted.

Write to Sabela Ojea at sabela.ojea@wsj.com; @sabelaojeaguix