During a debate in the House of Lords, Lord Howarth of Newport said the Psychoactive Substances Bill was so wide it could cover those who swing incense in churches, and even florists who sell highly perfumed flowers.
The former minister called for the Government to change the legislation so it is more targeted at dangerous drugs.
Lord Howarth said: "We really do not want to criminalise priests. The more vigorously the priest swings censer, the more incense is let loose into the body of the church.
"We have to be very careful we don't unintentionally criminalise either priests or florists, because of course flowers have psychoactive effects."
Lord Bates, who is leading on this legislation on behalf of the government, said the definition had been deliberately drawn widely to ensure a blanket ban in a fast-changing market.
The Advisory Council on the Misuse of Drugs (ACMD) has criticised the legislation. In a letter to Home Secretary Theresa May, it said the Bill was so widely drafted it could include substances that are "benign or even helpful", including some "evidence-based herbal remedies".
It claims a blanket ban could even damage the ability of scientists to carry out research on psychoactive substances.
The bill comes back to the House of Lords for its third reading on 20 July.