Retail sales fell by 1.2% between April and May, worse than economists had expected, figures from the Office for National Statistics have shown.
The ONS said that average store prices have risen by 2.8% over the year, which has been a significant factor in slowing growth.
Liberal Democrat MP Vince Cable said: “The economy has been kept going for a year on the basis of consumer debt, which was always artificial and unsustainable.
“The brutal reality of a hard Brexit is now starting to hit businesses and consumers.
“Unless the government takes a cross-party approach to Brexit, reflecting the need for compromise, we will inevitably see a continuing slowdown and possible slump in the economy.”