The environment was notably absent from Theresa May’s recent speech laying out her Brexit negotiating priorities. It was also rarely mentioned during the referendum campaign.

But worries that the UK could turn itself into a post-Brexit pollution haven have now been thrust front and centre by another often overlooked political actor: the European Parliament.

The parliament is often derided as a symbol of the Brussels’ gravy train, or more recently a boxing ring for UKIP’s MEPs. Yet it is an increasingly significant force in EU affairs, and has a long-held reputation for trying to enhance its own powers and for promoting greener policies.

Over the years, the parliament’s environment committee – a cross-party group of 68 MEPs – has led efforts to tighten car emissions, ban leaded fuel and the use of sealskins and, more recently, to secure strong climate change legislation.

It has also provided an entry point to the EU legislative process for less powerful actors like environmental campaigners, who struggle to have their voices heard by national policymakers or the European Commission.

EU Parliament can veto Brexit deal

But how and why will this institution make a difference to Brexit? The European Parliament’s consent is needed for any deal negotiated between the UK and the EU.

So not only does Theresa May’s government need to secure the support of 27 EU states for its final Article 50 deal, but also a simple majority of the 751 MEPs.

The parliament has now decided to flex its legislative muscles by outlining the areas it views as priorities in the upcoming negotiations. Maintaining environmental standards is apparently a red (or green) line for members of the chamber’s influential environment committee.

The committee’s paper “calls on the UK to continue to respect its environmental and climate change commitments”, adding: “Existing legislation which provides for commitments (financial, emissions reduction or of a political nature) cannot simply disappear on the day of Brexit and will require transitional measures.”

Crucially, air quality has been identified as a central issue for MEPs and is an area that the UK government continues to struggle with. Yet again, this year EU mandated air quality limits have already been breached in London and other urban centres (see photo).

But why would ‘Brussels’ care what kind of environmental rules the UK chooses to adopt post Brexit?

Dirty Britain would be a bad neighbour

There are two main reasons why UK environmental policy is of interest to its European partners. First, environmental pollution is transboundary: the UK gained its reputation as the dirty man of Europe in the 1970s and 1980s because its emissions from coal fired power stations led to acid rain in Scandinavia.

Its unpleasant habit of pumping raw effluent into the North Sea was also unwelcome. It is unlikely that our EU neighbours will want to see the UK return to its old habits of using prevailing winds and currents to dispose of unwanted waste in cost-efficient ways.

Second, environmental rules have major trade implications. EU policy was developed to even out differences across states, to prevent those with weaker environmental policies being able to secure competitive advantages. There are consequently good trade reasons for the EU to ensure that the UK maintains the same environmental standards.

No European country wants its farmers or carmakers, bound by restrictions on pesticides or emissions, to have to compete with a UK that relaxes such regulations or scraps them entirely.

The European Parliament can play a useful role in reminding EU negotiators of the importance of environmental regulations for the effective functioning of the single European market.

The parliament’s intervention adds another important voice to the Article 50 debates that may be useful to the Greener UK campaign that seeks to see UK standards maintained post Brexit.

Charlotte Burns is Senior Lecturer in Environmental Policy, University of York.

This article was originally published on The Conversation. Read the original article.