The upcoming European elections will be treated like a new Brexit referendum by many, according to a report.

Think-tank The UK In A Changing Europe also said the results could have a significant impact on the outcome of a Brexit deal with the European Union.

The elections, scheduled for May 23, are set to go ahead following Prime Minister Theresa May’s failure to get Parliament to pass her withdrawal agreement after seeking a Brexit extension to the end of October from Brussels.

Professor Anand Menon, director of The UK In A Changing Europe, said: “There is an irony that the upcoming European elections will be the most scrutinised, watched and dissected. And yet it remains far from certain whether – and if so for how long – any of the British MEPS will take up their seats.”

The report states: “Like it or not, convincingly or not, many people will portray the election as a proxy Brexit referendum. As for the EU itself, the elections will, obviously, have a bearing on the composition of the European Parliament.

“They will determine the balance of power – between pro-European and nationalist-populist forces, and between left and right–- and influence important decisions taken about key appointments to top EU jobs and the future agenda for Europe.

“All things being equal, British MEPs will play a part in those debates, even if their tenures do not last much longer than it takes for these initial decisions to be made.

“We face the prospect of British MEPs tilting the balance of power in a certain direction for long enough to shape key decisions, while giving up their seats before the consequences of those decisions become clear.”

The study also suggested the election results could have a bearing on the UK’s Brexit talks with the EU.

It stated: “Should, for instance, the Brexit Party gain a large number of seats, this may change the incentives of European leaders when deciding about whether to prolong British membership. A more fragmented and polarised parliament might slow down the process of agreeing any future trade deal.”

The report came as the Scottish Greens launched their election manifesto, promising to fight to stop Brexit.

The party, which described the election as the “most important European election we’ve ever had”, also promised to fight climate change and spread a positive message of hope in a bid to combat the rise of extremism across Europe.

Party candidate Maggie Chapman said: “These are the most important European elections we’ve ever had.  They’re Scotland’s chance to be heard – our chance to send a message that our democratic decision to stay in the EU must be respected.

“Scotland needs a Green voice in Europe to fight for a just and welcoming society and for the radical change that’s needed to tackle the climate emergency, which is the defining issue of our age. 

“No other party is prepared to take the bold action this global emergency demands. Greens also provide the antidote to toxic far right hate. The rise of the hard-right across Europe is deeply disturbing, but it cannot be countered from the centre. That’s why a Green wave is sweeping the Continent and why I’m determined to join it as Scotland’s first Green MEP.”

The party outlined its plans for combating climate change, including the creation of more green jobs, the development of faster and greener public transport and a call for a European-wide net-zero emissions target to be set. It also promised to defend freedom of movement throughout the EU and “stand against racism and xenophobia”.

Party co-convener Patrick Harvie added: “We’re confident that with our positive message of offering hope in troubled times, stopping Brexit and tackling the climate emergency we can win Scotland’s first Green MEP, building on recent election success both here in Scotland and throughout Europe.”