Four major butter makers have agreed to boost output by about 33 percent this month at the request of the farm ministry to meet surging demand for the Christmas season, the ministry said Thursday.

The four companies told the Agriculture, Forestry and Fisheries Ministry the same day that they plan to comply with the request, made last month, before demand peaks for the annual Christmas cake rush.

Last year's sweltering summer and a drop in dairy farmers reduced the production of raw milk, the precursor to butter.

The four firms — Megmilk Snow Brand Co., Yotsuba Milk Products Co., Meiji Holdings Co. and Morinaga Milk Industry Co. — will increase butter supply to 1,846 tons this month compared with 1,393 tons in November, the ministry said.

"Sufficient supply of butter will be ensured at stores before the Christmas season," a ministry official said.