Norway, which is not an EU member but enjoys more or less free trade with the union through the European Economic Area, is often advanced as a model for how the UK might thrive outside the EU. 

 

But Helgesen argued that for Norway, one of only three Nato members with a border to mainland Russia, it was difficult to be absent from the EU’s deliberations on security. 

 

“For Norway, not being at the table when policies so critical to our own security are determined is a challenge,” he said. “I cannot imagine the UK not being part of such discussions.”

 

He argued that the security situation in Europe had been transformed since British Prime Minister David Cameron agreed to hold a referendum on Britain’s continued EU membership last year . 

 

“Russia has annexed another country’s territory and is using military force to destabilize its neighbour. This is old-fashioned power politics that must not be allowed to succeed in Europe,” he said. 

 

The European Union was now much more important in determining how Europe responded to Russian aggression, he maintained. 

 

“This situation is very different from the Cold War, when Nato was the one organization that mattered for our security,” he wrote.

 

“Today, European policy towards Russia and Ukraine is primarily shaped within an EU framework. We have seen the EU, long known for a lack of strength in foreign policy, acting with remarkable resolve.” 

 

Helgesen began his lobbying mission with an interview in the UK’s Observer newspaper on Sunday, followed by an article in the Telegraph on Tuesday, and a speech to the pro-European think tank British Influence on Tuesday. 

 

Helgesen said Norway struggled with the economic and policy consequences of not being an EU member.

 

The country has implemented more than 10,000 European directives, some three quarters of the total, he said without having had any say in how the directives were formed.  

 

“Basically, with the exception of our agricultural policies, we are part of the same European integration process as the UK. But we do not have the right to vote in Europe,” he said. “I find it difficult to imagine the UK, with your global ambition, dedication and contributions, being comfortable with such an arrangement.” 

 

More important for Norway, he added, was Britain’s role in pushing for reform in the EU. 

 

“I think there is now a receptiveness in the EU for smarter regulation, less regulation and the EU caring more about the big things and less about the smaller things,” he told The Observer. “I think Britain has very important inputs to make in that process. And I also think that Norway – and Europe – is better served by the UK continuing to be a member.

 

The Observer quoted British Influence’s director, Peter Wilding, dismissing what he called "the Eurosceptic myth that Norway is the best [model] for a non-EU Britain”. 

 

“This is nonsense,” he said. “We now have the Norwegian Europe minister himself telling us to get a grip, get real and get involved in shaping Europe. Little England cannot be an option.”