"Intense" drought conditions are gripping parts of the UK after another month of scarce rainfall in some areas, experts said today.
The Government has declared an official state of drought in parts of eastern England after the country experienced the driest spring on record.
Farmers in drought-stricken areas have been hit with restrictions on water use, while others face controls in the next few weeks and there are fears of imminent hosepipe bans in Staffordshire, Nottinghamshire, Derbyshire and Leicestershire.
Severn Trent Water has told its customers they may face water restrictions in some parts of the region unless rainfall levels return to normal soon.
In its latest monthly summary on UK rainfall, river and water levels published today, the Centre for Ecology and Hydrology (CEH) said that a substantial proportion of eastern England saw less than a fifth of the normal levels of rainfall in May.
Some parts of Kent received just 4mm of rain during the last month.
While northern parts of the UK experienced "plentiful" rain last month - with Scotland recording its wettest May on record - most of it did not reach central and eastern England, compounding the previous two dry months, CEH said.
England had its driest spring in records going back 100 years, while England and Wales together had their second driest March to May in the record books.
The dry conditions have left Cambridgeshire, Lincolnshire, parts of Bedfordshire and Northamptonshire and western Norfolk officially suffering from drought.
In addition parts of the South West, South East, Midlands and Wales are experiencing near-drought conditions, the Department for Environment, Food and Rural Affairs (Defra) said.
The figures from CEH showed Cambridge received just half the previous minimum rainfall it had ever had in spring in records dating back to 1848.
The summary from CEH said intense spring drought conditions also characterised parts of Yorkshire, the East Midlands and Sussex and Kent, and that the "very arid spring" extended a deficiency in rainfall that can be traced back to December 2009.
While rain has helped rivers in northern Britain recover, others in the South West, parts of the Midlands and Wales and Kent have experienced exceptionally low flows, and waterways across southern and central England and Wales were below normal, the CEH said.
Current unsettled weather is set to continue through the weekend, but towards the end of next week south east and eastern England could return to drier, warmer conditions.
The Environment Agency said that continued dry weather would add further pressure on water resources and drought conditions may spread into central England and further east.
The agency has already asked nearly 100 farmers to stop abstracting water in Lincolnshire, Cambridgeshire, Bedfordshire, Northamptonshire and Norfolk, while 200 farmers in Suffolk face restrictions by the end of June.
And 27 farmers have also been told they will have to stop abstracting water by June 20 in the Walland and Romney Marsh areas of Kent to protect a nearby site of special scientific interest (SSSI).
Farmers in England's "bread basket" have said they fear it will be only a matter of weeks before drought conditions are extended across the whole of East Anglia.
The East Anglian branch of the NFU said the region's cereal producers have been badly hit, and in some cases fruit and vegetable growers were also struggling.
Livestock farmers are also facing shortages of grazing and are having to use up their winter resources far too early.
But in the drought-affected areas, Anglian Water and Cambridge Water said there is no threat to public water supply as they have enough to get through the summer.
Environment Secretary Caroline Spelman is set to convene a second drought summit in the next 10 days to discuss what can be done to tackle the issue.
Today she said: "Once drought status is declared then the Environment Agency will go into talks with farmers about how to conserve as much of the remaining water supply as possible, and how to use it more judiciously.
"But that applies to all of us. Everybody knows how to do that and actually now is the time," she told BBC Radio 4's Today programme.
With swathes of England facing drought, Friends of the Earth called for action to protect water resources, including stronger water efficiency standards for businesses, homes and appliances and tougher action on leaking pipes.
The green group also called for a duty on water firms to help less well-off customers save water, such as by fitting water-saving taps and showers, stricter planning controls on development to preserve local resources and an end to unsustainable abstraction licences.
Friends of the Earth's policy and campaigns director Craig Bennett said: "Despite growing water use and the prospect of drier summers successive Governments have failed to tackle the problem - leaving large parts of the nation facing the prospect of being left high and dry.
"Our water supplies have been taken for granted for far too long and now we're facing a drought that could devastate our wildlife, rivers and crops.
"Ministers must act to ensure we change the way we use our water instead of wasting it through badly designed buildings and appliances, poor planning and inadequate investment."
Fears have been raised that wildlife ranging from water voles to butterflies could be severely hit by the drought.
Dr Martin Warren, chief executive of wildlife charity Butterfly Conservation, said: "The hot dry weather has so far been quite beneficial to butterflies, they have emerged earlier and in reasonable numbers. But the drought is a potential threat because it dries up the food plants on which the caterpillars feed.
"When we had a prolonged drought in the summer of 1976 numbers crashed.
"We could see a devastating impact on butterflies if the drought continues for a long time."
The Environment Agency is currently monitoring rivers to ensure fish do not become stranded as water levels fall and to protect wildlife against low oxygen levels and pollution incidents, which can be worsened by a lack of water in rivers.
Shadow environment secretary Mary Creagh said: "People are concerned about the country's water situation and its impact on food production.
"Families are already feeling the squeeze from rising food prices, which hit a two-year high last month.
"The driest spring on record has already severely affected a fifth of the cereal harvest, which could lead to further price hikes for food and beer.
"The Government have dropped their plans for a Water Bill in this parliament, which means further delays in the changes we need to make to use water more efficiently.
"The Government needs to get a grip and reassure people that they have robust plans in place to deal with the drought."