However, the Italian submission to the UN records just a tiny amount of the substance being emitted.
Levels of some emissions from India and China are so uncertain that experts say their records are plus or minus 100%.
These flaws posed a bigger threat to the Paris climate agreement that US President Donald Trump's intention to withdraw, researchers told BBC Radio 4's Counting Carbon program.
Among the key provisions of the Paris climate deal, signed by 195 countries in December 2015, is the requirement that every country, rich or poor, has to submit an inventory of its greenhouse-gas emissions every two years.
Under UN rules, most countries produce "bottom-up" records, based on how many car journeys are made or how much energy is used for heating homes and offices.
But air-sampling programs that record actual levels of gases, such as those run by the UK and Switzerland, sometimes reveal errors and omissions.
In 2011, Swiss scientists first published their data on levels of a gas called HFC-23 coming from a location in northern Italy.
Between 2008 and 2010, they had recorded samples of the chemical, produced in the refrigeration and air conditioning industries, which is 14,800 times more warming to the atmosphere than CO2.
Now the scientists, at the Jungfraujoch Swiss air monitoring station, have told the BBC the gas is still going into the atmosphere.
"Our estimate for this location in Italy is about 60-80 tons of this substance being emitted every year. Then we can compare this with the Italian emission inventory, and that is quite interesting because the official inventory says below 10 tons or in the region of two to three tons," said Dr Stefan Reimann, from the Swiss Federal Laboratories for Materials Science and Technology.
"They actually say it is happening, but they don't think it is happening as much as we see.
"Just to put it into perspective, this greenhouse gas is thousands of times stronger than CO2.
"So, that would be like an Italian town of 80,000 inhabitants not emitting any CO2."
The Italian environment agency told the BBC its inventory was correct and complied with UN regulations and it did not accept the Swiss figures.
Another rare warming gas, carbon tetrachloride, once popular as a refrigerant and a solvent but very damaging to the ozone layer, has been banned in Europe since 2002.