Russia appears prepared to create “environmental havoc” by sailing unseaworthy oil tankers through the Baltic Sea in breach of all maritime rules, the Swedish foreign minister has said.

Speaking to the Guardian during his first visit to London since Sweden became a Nato member, Tobias Billström called for new rules and enforcement mechanisms to prevent the ageing and uninsured Russian shadow fleet causing an environmental catastrophe. About half of all Russian oil transported by sea passes through the Baltic Sea and Danish waters, often operating under opaque ownership, and using international waters to try to avoid scrutiny.

The fleet generates a huge amount of revenue for Russia’s war machine, bypassing western sanctions that try to block access to insurance if Russia sells the oil above $60 a barrel. In practice as little as 20% of Russian oil is sold below the price cap.

Foreign ministers from the eight Nordic-Baltic grouping of countries met on the strategic island of Gotland a fortnight ago to discuss how to tackle the Russian fleet.

“We will all be affected if there were a major problem arising from a collision or oil leakage from one of these ships, which also in many cases are not seaworthy, or very close to not being seaworthy,” Billström said.

“The fact that they are transporting oil, which fuels Russian aggression against Ukraine is bad enough. But even worse is the fact that Russia doesn’t care one bit, apparently, about the fact that these ships could cause major environmental havoc in seas, which if you take the Baltic Sea is sensitive as it is.”

He said every state that was a member of the International Maritime Organisation had a responsibility to uphold IMO rules and regulations, and had the right to ask the captain of a ship not deemed seaworthy to take action before leaving port.

However, some Nordic countries are anxious about the Russian reaction if they did intervene since it may add to Moscow’s belief that the Baltic Sea is being turned into a “Nato lake”, cutting Russia’s access to the sea from St Petersburg and other ports such as Kaliningrad.

International law allows ships to be interdicted if they are deemed to be improperly flagged, but some of the law is unclear. Billström agreed that Nato members could hardly risk being seen to be acting like the Houthis in the Red Sea by defying freedom of navigation.

The US is also anxious in an election year about the possibility of an oil shortage sending prices at the pumps through the roof.

The addition of Sweden and Finland to Nato had, Billström said, changed the strategic situation in the Baltic Sea since it left Russia as the only country with a Baltic coastline not a member of the military alliance. Sweden has already moved to strengthen the Swedish presence on Gotland.

Sweden, which has worked alongside Nato in Libya and Afghanistan, has submarine space and cyber-capacities that represent a significant boost to the alliance’s capability. It also has a civil defence capacity that is seen as the envy of Europe. The former UK armed forces minister James Heappey said he kept a copy of the Swedish civil defence manual on his desk as a model for what Britain should emulate.

Billström said joining Nato felt like Sweden was coming home, and with the country’s close defence links with the UK intended to join the more hawkish end of Europe. He said history showed Russia did not change behaviour unless it was defeated in war and brushed aside suggestions of satisfying Vladimir Putin with parcels of Ukraine.

“Putin has made it absolutely clear what his goals are – the total annihilation of Ukraine,” said Billström. “He doesn’t believe Ukraine has right to exist as a state. This is not about ceding individual plots of land, and any thoughts about the frozen conflicts would be very dangerous, because it will only allow Putin more time to rebuild his armed forces, trying to push towards Kyiv. No, we should do exactly the opposite.”

Billström favoured greater Nato coordination of arms supplies, including air defences, but added that political will was needed.

He pointed to the example of the Nammo arms factory in Karlskoga that now has five shifts running 24/7, with the goal of tripling ammunition production by the end of 2024, compared with 2022.

“This isn’t about production capabilities. This is about putting your will into it,” Billström said.

“Decisive military victories in the battlefield are critical because nothing else is going to change the political course of Moscow or the Russian leadership.”

That included, so far as he was concerned, making Moscow understand that Ukraine was entitled to attack energy refineries inside Russia. “It has to understand there are no shielded installations inside Russia with which to fund its illegal aggression against Ukraine,” said Billström.

Like all foreign ministers, he said he was wary of the implications of a Trump presidency had for Europe, Nato and Ukraine, but doubted the bulk of the Republican party had succumbed to pro-Russian propaganda.

Billström said the Republicans had a tendency to turn isolationist during a Democrat presidency, but he added that it was necessary for Europe to show it understood the connection between Ukraine and the Indo-Pacific region.

He said there was also a clear link in this with Iran and the Middle East. “We can now see how all authoritarian states are working together and helping one another. It means we are at a very, very crucial point, almost a crossroads in human history, where we have to think about what would happen if Russia wins in Ukraine.

“If Putin won, it will probably mean the whistle will blow in the Indo-Pacific, and we will see greater Chinese assertiveness in the Taiwan strait.

“We want the US to be interested in what’s going on in our part of the world. We have to be interested in what’s going in theirs. We in Europe have to see how this is all interconnected.”