"It's not certain that it would be a good idea to let a big country into this organization," Norwegian European Affairs Minister Elisabeth Vik Aspaker told daily Aftenposten.
"It would shift the balance, which is not necessarily in Norway's interests," she added.
The Scandinavian country is not a member of the European Union but it has access to Europe's lucrative inner market via its membership in the European Economic Area (EEA), which groups all EU members and three of the four EFTA members (Norway, Iceland and Liechtenstein, but not Switzerland).
While the arrangement has been criticised in Norway because it means Oslo must apply European regulations without having a vote at the table, pro-Brexit campaigners pointed to the model as an example for Britain to follow should it leave the EU.
Britain was a founding member of EFTA in 1960, a free trade organization that was an appendage to the European Economic Community, the forerunner of the European Union. In 1973, Britain joined the EEC.
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By opposing a British return to EFTA -- where decisions are made by consensus -- Norway would effectively block London's chances of accessing the European market via the EEA, since only EU and EFTA members can be part of the EEA.
Before the summer break, the Norwegian government set up an inter-ministerial working group to assess the consequences of Britain's EU exit. It is not yet known when its conclusions will be submitted.