Launched in 2010 by Prime Minister David Cameron and his Swedish counterpart Fredrik Reinfeldt, the NFF is to be held later this year in Finnish capital Helsinki, although no date for the meeting has yet been set.
Originally known as the UK-Nordic-Baltic Summit, the group of nine nations meets annually to discuss issues of common interest, including green energy, arctic policy, the digital divide, sustainable growth and the ageing population. It currently consists of seven EU countries - the UK, Denmark, Estonia, Finland, Latvia, Lithuania and Sweden - and two non-EU countries, Iceland and Norway.
Stressing that Scottish membership "would be a decision for the group", the FCO spokesman said that because the NFF - unlike the EU - was "not governed by complex rules and articles", Scotland's "shared interests" would make it "likely to be welcome" in the event of a Yes vote in September.
However, a Scottish Government spokeswoman declined to say whether it would seek to join the NFF after independence, saying instead that it "intends that Scotland will also seek a closer relationship with [formal Nordic-Baltic inter-governmental group] the Nordic Council".
"Scotland has key shared interests with our geographical neighbours in the North Atlantic, such as Iceland and Norway, and a common interest in the Arctic and High North," she said.