AVA- Waste consultancy Eunomia estimates official figures over-state the quantity of plastic packaging sent for recycling by about a third.
Much of what does go into the waste stream may be of such poor quality it cannot be re-used, its report said.
An industry spokesman said he was "very confident" of the accuracy of the data from packaging firms.
But Eunomia argues that the industry's figures simply do not tally with the amount of plastic actually in the waste stream.
And it says packaging firms contribute a small fraction of the £2.8bn burden on local authorities of dealing with waste.
So who does the calculations? And who is making sure that companies get it right?
Well, packaging firms have to take part in government-approved schemes under what is known as "producer responsibility".
This obliges them to purchase a credit - a Packaging Recovery Note (PRN) - from a recycling firm to contribute to improving recycling.
Defra says the scheme raised £50m in 2016. The cash was to be used for "capacity building" in the recycling system through increasing collection and processing of recyclables.
But critics say the scheme is so opaque it is hard to tell exactly how the money is spent.
Local councils, which have to run waste collection and litter services, complain they do not see a penny of it.
The row goes to the heart of the government's current review of plastics and waste. Green campaigners want ministers to adopt the sort of deposit and return schemes on drinks containers that are seen across northern Europe.
This system is transparent because every container going on to the market has to be registered for the deposit. So the tally of recycled bottles and cans is based on real numbers, not estimates.
The packaging industry is urging ministers to stick with the current PRN scheme, which it says is cheaper. It is offering to make the system more transparent and to increase the amount raised for improving recycling.
The Environment Secretary Michael Gove is expected to make a decision on the issue after Easter.
Official statistics say that in 2016 the UK produced 2.26 million tonnes of plastic packaging waste, and recycled almost 44.9% of it.
But Eunomia's Dominic Hogg countered: "No-one believes these figures."
He said when packaging was placed on the market it is clean, dry and free from extra materials such as labels.
But when the quantity of plastic collected for recycling is measured, the weight is inflated by moisture, contaminants and labels.
Another problem may be that volumes of plastic packaging placed on the market are based on estimates provided by the packaging industry itself.
These firms, Eunomia claims, have little incentive to ensure accurate data because the more plastic they put on the market, the bigger their recycling bill through the PRN system.