It was the wettest year on record for England and the third wettest for Wales, but Scotland experienced only its 17th wettest year and in Northern Ireland it was the 40th wettest.
Persistent wet weather led to rainfall of 52.4in in 2012, just 0.26in short of the highest recorded annual total set in 2000, according to Met Office records, which stretch back more than a century.
And preliminary evidence from the Met Office suggests the UK could be getting slightly more annual rainfall than in the past and it may be falling in more intense downpours.
Almost 8000 homes and businesses were flooded last year as drought in early 2012 gave way to repeated storms and bands of rain, with the UK seeing record-breaking monthly rainfall in April and June and the wettest summer in a century.
Farmers' crops were hit by the unusually wet summer, while much of the country's wildlife struggled.
Newly published figures show four out of the five wettest years ever recorded have occurred since the beginning of this century.
The top five wettest years in the records dating back to 1910 are 2000, 2012, 1954, 2008 and 2002.
The UK as a whole had 15% more rainfall than average during the year, with England experiencing almost one-third more rain than normal as it recorded its wettest ever year.
In Scotland, when the wet weather did arrive, it came in force, with Tyndrum, in Perthshire, seeing the heaviest rainfall of anywhere in Britain.
Between December 19 and 20, 6in of rain fell in just 12 hours – more than half the average rainfall for the entire month.
The official forecasters said the UK was getting wetter in recent decades, with average long-term rainfall increasing by about 5% between the periods 1961 to 1990 and 1981 to 2010.
The occurrence of extreme days of rain, in which large amounts fall in intense downpours, also appears to have become more frequent.
The Met Office said rising global temperatures could be playing a part in increasing rainfall, as a warmer atmosphere can hold more moisture and increase the potential for heavy rain.
"The world has seen temperatures rise by around 0.7°C since the beginning of the industrial revolution, which would equate to around a 4% increase in moisture in the atmosphere.
Changes in sea surface temperatures as a result of natural cycles and a fall in the amount of Arctic sea ice could also be playing a role, but more research is needed to establish what their impacts were, experts said.
The Met Office's Julia Slingo said the trend of more extreme rainfall events was one being seen around the world.
Professor Nigel Arnell, Walker Institute director at Reading University, said last year's weather fitted a pattern which has seen rainfall increase in recent decades in many parts of the northern hemisphere.
"While rainfall varies naturally from year to year and decade to decade, there is increasing evidence the build up of greenhouse gases in the atmosphere is starting to affect rainfall across the globe," he said. "That means we are likely to see flood frequency increase further."
He said wet winters seen in northern Europe around once every 20 years could happen almost every other year by the end of this century, but curbing greenhouse gases which warm the climate could reduce the increasing risk of floods.
Friends of the Earth head of policy Mike Childs said experts expected to see extreme weather events such as intense rainfall become more common as global warming takes hold.
"So far, the world has warmed by an average 0.7°C above pre-industrial revolution levels – if temperatures rise by the 4°C scientists widely predict then we can only begin to imagine the impacts on our lives and livelihoods," he said.
"But there is still time to tackle climate change."
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