The Food Standards Agency has advised that the bottles contain potentially harmful levels of methanol which could have serious health effects, including blindness, if consumed in large quantities.
No cases of ill health have yet been reported as a result of the scare.
Itís the second major fake vodka alert from the FSA this year, following the discovery of counterfeit bottles of Glenís vodka on sale in many parts of the UK in the spring.
In the latest scare, no fake bottles of the Spar own-brand have found their way into Spar stores.
Spar has told the FSA that the only legitimate route to market for Sparís own-label is through its stores, which means any bottles offered to non-Spar stores should be treated with great caution.
Local authorities across the country are being asked to check for counterfeit bottles and take action where necessary.
The counterfeit Spar Imperial vodka has a hint of an acetone smell, similar to nail varnish.
Counterfeit bottles are identified by the code QI:1445c and a smudged inkjet code that looks like 102234 04/08/02
Legitimate bottles are marked with 700ml66mm followed by two symbols and then the numbers 8809.
Only genuine bottles have a lot code on the bottle neck.