British MEP Emma McClarkin says the EU and Belgium "must look at their political processes" following the failure to agree the CETA trade deal with Canada by Monday's deadline.
Her concerns are echoed by Alexander De Croo, the Flemish liberal deputy Prime Minister of Belgium, who warned of the consequences of the Walloon government continuing to refuse to give the thumbs up to the signing of the deal.
The Walloon Parliament is opposing CETA, despite not having expressed its concerns during the seven year negotiation process and even though the treaty text has been available for two years.
On Tuesday, European Council President Donald Tusk was still to decide whether the CETA signing can go ahead at a summit in Brussels as planned later this week.
With that looking less likely by the hour, McClarkin, the Conservative international trade spokesperson, said: "The objections of the Walloon Parliament are internal political concerns and we are disappointed that they have chosen, for narrow protectionist reasons, not to allow the agreement to go ahead.
"Canada is a country with whom we share values and principles. If we cannot agree what is regarded by many to be one of the highest quality agreements ever negotiated, it questions the ability of the EU to deliver new opportunities for growth and jobs.
"Other potential trading partners will look at events of the past few days and wonder whether it is worth investing years of time and effort negotiating a deal with the EU, only for it to be held up, or even struck down, at the final hurdle.
"The treaty cannot be reopened and we do not support going back with further requests, but all measures outside of that are possible in terms of clarifying the agreement.
"CETA will eliminate 98 per cent of tariffs between the EU and Canada, save EU exporters €500m a year and increase trade by 20 per cent, so we must overcome these difficulties for the sake of businesses and communities across Europe. I am confident we will."
Speaking on Tuesday, De Croo warned the impasse could mark the start of a "slow breakdown of the European project."
"The European Union has been negotiating for the past seven years. During this time there wasn't the slightest criticism from Wallonia. Two years ago the German Socialists raised the issue of arbitration that the Walloon leader Paul Magnette is talking about now.
"I can't help but have the impression that this is all a political game in which Magnette is risking the reputation of Belgium and of Europe. However, with a population of four million, you can't hold 500 million Europeans hostage. There comes a time when it has to stop."
Further comment on the row came from ECR group Chair Syed Kamall, who said, "The free trade agenda in Europe is on life support, and countries across the planet that are looking to open trade with the EU will be wondering whether it is worth years of effort.
"The Walloon Parliament was given the power to reject this agreement and it is only right that their decision was respected, but it is also only right that they now understand the consequences of their decision."
Elsewhere, Flemish S&D group MEP Kathleen Van Brempt said that she has respect for what the Walloon government is doing.
Van Brempt believes that Wallonia's continuing refusal to approve the free trade treaty with Canada is a "game-changer."
"After this incident the political debate about trade treaties will never be the same. It will be a lot better," she said.
The Walloon government, she said, has "put a very important debate at the top of the political agenda."
However, BusinessEurope President Emma Marcegaglia said Europe's business community "calls on all parties to live up to their responsibility in defending the collective interest of Europeans and protect Europe's credibility in the world."
She added, "We still can and we have the duty to urgently bring home the best trade agreement the EU has ever negotiated.
"Going forward we will have to rethink our governance and to make sure that a small minority cannot take the whole continent hostage for short-sighted political considerations."