Norway's Foreign Minister Borge Brende says it makes sense for the UK to stay in the European Union, where it "can have more influence" than outside.
Norway is not in the EU but enacts most EU legislation in order to maintain access to the single market.
"Europe without Britain I don't think is as strong a Europe as with Britain inside," Mr Brende told BBC Radio 4's Today programme.
The UK will hold an in/out referendum on EU membership by the end of 2017.
UK Prime Minister David Cameron has launched a diplomatic campaign to garner support from other EU leaders for his EU reform plans.
New curbs on migrant benefits are a priority for the UK Conservatives, but they also want to cut EU bureaucracy, give national parliaments a bigger say over EU laws and remove market barriers in key areas such as services.
Single market 'so important'
Eurosceptic opponents of the UK's membership argue that being outside would enable the UK to control immigration from the EU and trade more freely with major powers outside the EU.
Mr Brende said Norway was "among the fastest in Europe" in implementing EU directives, "because the single market is so important", with almost 80% of Norwegian exports going to the EU.
The foreign minister is from Norway's Conservative Party, the country's main centre-right party.
Norway is in the European Economic Area (EEA), along with Iceland and Liechtenstein, which allows them to trade in the single market.
Some British Eurosceptics look to Norway's position as a model for the UK if it were to leave the EU.
"In the EEA we have to implement all EU directives... we're not around the table when they're discussed in Brussels," Mr Brende said.
"We see Britain as an important voice also in the EU, we know Britain is now seeing a recovery in its economy, and we want to see the European economy also revive…
"Part of this is also addressing the bureaucracy in Brussels, in a no-nonsense manner. I think Britain is that kind of voice in the EU...
"Britain also can have more influence inside the EU than outside."
When asked about trade with the rest of the world, Mr Brende said a future EU-US free trade deal, currently being negotiated, could be "a challenge" for non-EU countries like Norway - and the UK if voters said "No" to EU membership.