The figures come from the latest Agriculture and Horticulture Development Board Market Survey, which also showed exports to France up by 7% over the same period.
At the same time the total amount of chilled and frozen lamb and mutton imported into the UK from New Zealand rose to 28,000t in the first quarter, a rise of 4% of 2009.
"It's a small amount in itself, said John Mabb, UK market manager for Meat and Wool New Zealand, "and reflects the fact that UK retailers tend to get nervous about securing supplies for Easter, with some UK lamb being replaced.
But long term it could be more significant. I hear industry leaders in the UK talking about high prices and how these should remain so, but a structural change is going on where the flock size across Europe is falling. That should make the UK industry ask lots of questions about supplying major retailers."
Mark Topliff, senior analyst for EBLEX, said: "Because of a smaller breeding flock, the number of lambs available for slaughter is significantly lower than last year.
"However, other factors have accentuated the decline in slaughter numbers, such as lambs taking longer to reach target slaughter weights as a result of the unfavourable winter, and firmer prices and more positive sentiment within the industry may have resulted in a larger number of ewe lamb retentions."