Adding nine countries to EU to cost existing members more than €250bn

Expanding the size of the EU to include nine new countries including Ukraine would cost the existing members more than €256bn (£220bn), internal calculations have revealed.

The knock-on effect would be to turn many countries that currently enjoy net financial benefits of the EU into net contributors.

The vast cost of enlargement has been disclosed as 51 European leaders descend on Granada in Spain for a gathering of the European Political Community and to discuss the next steps for the nine neighbours queueing up to join the EU.

“All member states will have to pay more to and receive less from the EU budget; many member states who are currently net receivers will become net contributors,” the paper by the secretariat of the EU council, leaked to the Financial Times, states.

Ukraine, by far the largest of the nine countries that have been accepted as potential candidates, would be entitled to €186bn over seven years, according to the paper. That would come on top of current lower estimates for the cost of reconstructing Ukraine, which were put at about €400bn this year by the World Bank.

Enlargement has become one of the most urgent topics for the EU, with leaders meeting on Friday to discuss how to direct the debate to come on key issues including the budget, the number of seats in the European parliament, the future of the common agricultural policy and whether an expanded bloc could continue with unanimous voting in certain areas.

Also being debated is whether the EU should proceed with a two-speed process, allowing member states phased entry to the bloc, or whether it should be all or nothing.

Earlier this week the EU’s chief diplomat said he opposed those who favoured a gradual membership process, saying it would be impossible to implement. “Membership is membership. Full stop,” he said at a meeting in Ukraine.

One senior diplomat told the Guardian the budget was expected to be the single most contentious subject and needed to be settled by 2027, when the next financial cycle would begin. That way the EU could show it was ready, removing any excuse to delay further discussions over whether and how quickly Ukraine, Moldova and the western Balkan states could join.

Earlier this year the president of the European Council, Charles Michel, said the deadline should be 2030 but the diplomatic source said such a date was “random” and made no sense. A target of 2027 would, they said, concentrate the minds of EU leaders in the next two years and provide a framework for a real – rather than conceptual – discussion.

The leaked document estimates the budget would increase by 21% to €1.47tn if all nine countries were to join. That would involve significant increase in contributions for Germany, France and the Netherlands, with transition periods necessary to scale up the funding.

The amount spent on agriculture would also shift, with Ukraine entitled to €95bn over seven years, another cost member states would have to consider. Ukraine has argued that as a world leader in the grain, sunflower oil and poultry markets, its membership would strengthen the EU’s food security.

Another key fund, known as the cohesion fund, which provides money for infrastructure in less developed countries, would also be significantly affected by enlargement. Under the current financial formula, the Czech Republic, Estonia, Slovenia, Cyprus, Malta and Lithuania would no longer be eligible for the funds.

Last month the European Commission president, Ursula von der Leyen, said the EU must immediately prepare for radical changes needed for Ukraine and other countries to become members of the bloc.

There are concerns that while the EU has set out reform goals for Ukraine, Moldova and the seven other countries queueing to join the bloc, it has yet to provide detailed proposals on changes needed in member states.