"We do not want this at all - it is meat make-up," said Jan Bertoft at the Swedish Consumer's Association (Sveriges Konsumenter).
Thrombin is a coagulation protein which together with the fibrous protein fibrin can be used to develop a "meat glue" enzyme that can be used for sticking together different pieces of meat.
EU countries voted to approve the use of the enzyme on Monday.
Despite clear labelling of meat products, there remains a concern that consumers will be fooled as it is not clear from the appearance of the product whether it is constructed from different pieces of meat or not.
The additive can for example be used to put together small parts of pork tenderloin to make the product look like a whole fillet.
"The problem is that it looks like real meat. It is the dishonesty in it that makes us think that it is not okay," Bertoft said.
The approval of thrombin has also come in for criticism from some Swedish politicians.
"To use Thrombin in meat is a way of misleading consumers, to present something as better than it actually is," said Åsa Westlund, a Social Democrat MEP.
Westlund has been involved in the process to develop new EU legislation covering food additives which will come into force in the beginning of next year.
"If it had been in force today, then this would not have been allowed. That is my view," she said.
But Gunilla Henrysdotter at the Swedish National Food Administration (Livsmedelsverket) argues that it is not for certain that the new legislation would have rendered thrombin illegal.
"It would be approved in the future as well," she said.
The decision to approve thrombin was taken by a Standing Committee on the Food Chain and Animal Health (SCFCAH) on Monday. One country voted against and one abstained. All the other countries, including Sweden, voted in favour.
The most important issue raised by Sweden was the proper labelling of products containing thrombin, according to Evelyn Jansson-Elfberg at the Food Administration.
"There is no danger in eating it, but the risk is that the customer will pay an excessively high price. It is the misleading aspect of it all that we have reacted against," she said.
Story continues below…
Sweden, and several other countries, have thus argued that thrombin should be classed as a food additive instead of a processing aid.
This line of reasoning was accepted and means that thrombin will only be able to be used in products in which its content its clearly declared.
The products will read "composite meat product."
Thrombin can be made from blood taken from either cows or pigs, and this information must also be clearly shown.
Products containing thrombin will not however be approved for use in commercial kitchens.