The comments come after a member of Perkins’s constituency contacted him after failing a test.
Licensee Keith Bannister, of Harley’s Bar in Staveley, Derbyshire, believes the way the operation was carried out was “entrapment”.
Bannister said that on 3 November his barstaff were tricked because the mystery shopper appeared to be dating a 30-year-old man.
“My member of staff said that she didn’t think a man who looked around 30 years old would be going out with someone under 18, so she served her,” he said.
“The British pub trade is being targeted by over-zealous people.”
In a letter to Derbyshire County Council, Perkins wrote: “It would appear to me that, far from protecting the public from irresponsible bar sales and ensuring that young people do not have inappropriate access to alcohol, trading standards has, in this case, targeted a pub in what might be considered to be a ‘sting’.
“I know that at one time trial purchasers were obviously below 18, whereas now there appears to be a deliberate attempt to trick landlords and barstaff.
“I would be grateful if you could look again at the evidence for the whole of that evening [in Harley’s Bar].
“I would also like to know if you feel that, by appearing to be a couple, the mystery shoppers were in fact outside your own terms and conditions for operations.”
The county council said the operation was carried out by Derbyshire police.
A force spokesman said: “The safety of test-purchase operations is paramount and different tactics are used for operations.
“We are satisfied that these operations are carried out ethically and legally.”
Serve Legal carries out 5,000 tests a month privately for around 50 pubcos seeking to improve their pubs’ ID-checking performance. Its director Ed Heaver said that he is getting more requests from clients to carry out different tests.
He said: “Clients are asking us to do slightly different tests, whether it be checking sales by proxy or checking for the correct ID. A lot of operators are performing much better in asking for ID.
“In this instance, the local authority is looking at other ways that kids are getting alcohol. All retailers need to be up to scratch with this and check if they need extra training.”
Trade consultant Michael Kheng, who has been campaigning for under-18s that buy alcohol to be prosecuted, added: “If you get caught once, you will be targeted again and again.
“No matter who it is, you should always ask for ID.”
Jonathan Smith of Poppleston Allen said: “There is a trend among some authorities to send test purchasers with people over 18. We heard of a situation where a volunteer was 17 and with two trading standards officers aged over 30. While it could be described as slightly underhand, it is the appearance of the volunteer that is the question.
"Trading standards may be criticised, but it is unlikely to help in the defence of the person who made the sale that they were with two older people.”