PARIS (Reuters) – More than 18 months after global regulators adopted emissions rules for commercial aircraft, the European Union is embroiled in an internal debate over how they should be applied in a row that could have consequences for current Airbus models.

The European Parliament and EU member states will meet on Wednesday to try to bridge differences over how far European authorities should be limited by last year’s pact at the United Nations’ International Civil Aviation Organization (ICAO).

Last year’s Montreal agreement sets limits on emissions from all new aircraft from 2020 and will be phased in for deliveries of existing models of aircraft from 2023, but environmentalists have said it does not go far enough.

The debate is being rekindled as policymakers ponder the future of the European Aviation Safety Agency (EASA), which is responsible for aircraft certification standards for 32 EU and non-EU nations.

Under a proposal by the European Commission to reform the Cologne-based agency, EASA would be able to impose CO2 emission standards stricter than those agreed in 2016 at ICAO.

However, EU member states have pushed for that option to be taken out so that EASA would only be able to implement the standards agreed at the U.N. aviation agency, and no more.

A Commission spokesman declined to comment on the talks between the Parliament and member states and said its position had been set out in the original proposal.

Under the agreement at ICAO that followed six years of talks, some current-generation aircraft like the A380 delivered after 2028 would need a costly upgrade, although it remains uncertain whether it will be produced until then because of slow sales.

Some, like the A330 freighter, would no longer be delivered.

The latest debate looks set to reopen friction between environmental campaigners and Airbus, whom they accuse of leaning on the Commission to weaken its policy with the backing of France, where the planemaker is based.

In the run-up to Wednesday’s meeting, environmental group Transport and Environment (T&E) supplied emails between Airbus and the Commission obtained through a freedom of information request, which it said indicated Airbus had dictated policy by being allowed to insert comments directly into an EU draft.

The policy put forward by the EU at the ICAO talks was less stringent than the one eventually adopted with U.S. support.

“Now we know: when it comes to climate Europe lets Airbus write its own rules, rendering them ineffective. It will happen again on Wednesday unless EU countries stand up to Airbus and their shareholder governments (France, Germany and Spain) and enable Europe to decide on its environmental laws,” Andrew Murphy, aviation manager at T&E, told Reuters.

A spokesman for the Commission said it always “consults a wide range of stakeholders, including governments, industry and non-governmental organizations” when preparing Europe’s ICAO negotiating position.

“It is normal that, in that context, there have been contacts with Airbus, which is the biggest producer of airplanes in Europe,” Enrico Brivio said.

Airbus denied exerting any pressure on EU decision makers.

“It is completely normal for us to engage in dialogue with the European Commission to relay our opinion on appropriate matters,” a spokeswoman said.