Most of the country, 71.3 per cent, is now experiencing a flash drought caused by a combination of very low rainfall and higher temperatures.
That has risen since late July, when almost half the country was declared to be in drought.
The latest update put 45 million people in a drought area and 27 million living under water restrictions.
Britain is in the grip of its fifth heatwave this year and England and Wales have provisionally recorded their driest July in 190 years.
Southeast England received just one per cent of its expected average rainfall.
"We know how challenging this summer has been ... We are stepping up our support including working to make it easier for farmers to build more on-site irrigation reservoirs," Water Minister Emma Hardy said in the statement.
Rivers, reservoirs and groundwater levels continue to decline while the continued hot and dry conditions are increasing the risk of wildfires, the government said.
An estimated 2877 people in Britain have died from heat-related causes this year, UK health authorities said last month.
The heat is also impacting breeding birds, amphibians, and freshwater fish stocks, the government said.
