Brexit will force the European Union’s remaining 27 countries to spend billions of euros on cutting carbon emissions more deeply to compensate for the UK leaving, according to experts.

The UK will be included in a Brussels communique on 20 July, setting out individual targets for EU signatory states to meet a bloc goal of a 40% emissions cut by 2030, as pledged in Paris last year.

But once Britain invokes article 50 and begins its journey to the EU’s exit door, the bloc will have to draw up new CO2 plans for the other 27 countries.

This is because the UK is a large economy with a relatively advanced green sector, and its departure will oblige each EU state to raise their climate ambition by between 0.2-1.7%, according to an analysis by Climate Action Network (CAN) Europe.

The study found that the counties whose climate commitments would be most affected by the UK’s departure were Portugal, Slovenia, Malta, Greece, Cyprus, Spain and Italy. Wendell Trio, CAN Europe’s director, said that Brexit could be a spur to other EU countries taking on greater climate commitments.

“It doesn’t necessarily have to be something bad,” he said. “It just means the other countries will need to compensate for the changes that might be brought about by the UK leaving.”

The analysis did not look at the knock-on cost effects caused by extra climate mitigation measures, such as an expansion of renewable energy infrastructure or energy efficiency programmes.

In the long term, spending on clean energy is usually seen as a good investment. In the short term though, costs could run to several billions of euros, according to Bill Hare, a former Intergovernmental Panel on Climate Change (IPCC) led author and the founder of the Climate Analytics consultancy.

“The costs could run to several billions in gross terms, although the net costs would probably be lower,” he told the Guardian. “If the UK completely separates from EU climate policies in every sense, there will be consequences. But if the EU and UK remain entangled in a constructive way, going forward with policies like the emissions trading system, then the differences may not be so extreme.”

The first review of climate commitments made under the Paris agreement will come in 2018, and this is already being viewed as an opportunity for a redistribution of Britain’s contribution to Europe’s plans.

The European commission refused to comment on the new analysis but one EU source told the Guardian that 2018: “will mostly be aimed at those countries like the US which have 2025 targets but it is also an obvious incentive to those with 2030 targets to rethink whether they can be more ambitious.”

The greatest challenge to revisiting the “burden sharing” of greenhouse gas reductions may come from EU states such as Poland, which have drawn a red line around any further climate action.

“The percentages [in the analysis] sound in the right ballpark and it will not be a massive increase,” Hare said. “But given that, for some countries in the EU, every megatonne of CO2 seems to be contested, I am sure that it will be fertile ground for more political trouble.”

The CAN analysis was based on an EU decision in 2014 that allocated CO2 cuts to poorer states on the basis of their GDP per capita. For richer states, the calculation was done by combining GDP per capita with the potential for cost-effective emissions reductions.