But he insisted that we were at the bottom of the cycle, and the Champagne market would "bounce back."
"The U.K. has finally exited recession and a growth in wages may well filter through," he said.
"There has been a shift towards sparkling wine, but it's quite clear that consumers differentiate between everyday celebrations – when Prosecco might suffice – and special occasions, where Champagne continues to own the moment."
In contrast to Champagne, sparkling-wine alternatives like Spain's Cava and Italy's Prosecco have received a welcome boost from the downturn.
Between 2008 and 2013, this sparkling wine segment grew by 45 percent in the U.K., according to Mintel. Its value is expected to have hit £770 million ($1.3 billion) last year, a 6 percent year-on-year rise.
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The growing popularity of Prosecco – made in the Conegliano and Valdobbiadene regions of Italy – has made headlines, but Mintel found the growth was in fact being driven by its Spanish rival.
Cava accounts for around 50 percent of off-the-shelf sparkling wine sales in Britain, whereas its Italian rivals – including Prosecco, Asti, Moscato and Frizzante – account for around a third.
Fizzing growth elsewhere
And it wasn't just British consumers that have shunned Champagne. Shipments to Germany, Italy, Switzerland and Spain – which are among the wine's top 10 export markets – fell in 2013.
Some countries, however, showed an increasing appetite for the premium fizz, with shipments up by 6.75 percent in Japan, 11.4 percent in Australia and 14.15 percent in Belgium.
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"There are plenty of markets around the world where the idea of Champagne is really taking off," Wine Intelligence's Halstead added.
Champagne had always been a popular in Japan, he said, but a new generation of consumers were starting to drink it more regularly on special occasions.
Whereas in Australia, he said the sparkling wine market had "exploded." "It's from a relatively small base now, but is an incredibly important for Champagne," he said.
Australia is currently the sixth largest importer of Champagne, after Belgium, Japan, Germany, the U.S. and the U.K.
But U.K. Champagne Bureau director Francoise Peretti stressed: "The U.K. has been Champagne's number one export market for the past 18 years, and that is not about to change."