Christine Lagarde has championed the UK's membership of the European Union, and called on Europe to counter the populist and insular mindset sweeping the continent.
In a speech in Vienna this morning, the managing director of the International Monetary Fund (IMF) said there was a "clear case as to how the UK has benefited — and will continue to benefit — from its membership of the EU."
The comments come hours after the IMF delayed the publication of its eagerly anticipated economic analysis on the impact of Brexit after the death of Labour MP Jo Cox. Last night, Lagarde refused to answer questions on the subject at a dinner of Eurozone finance ministers.
Instead, the IMF's analysis will be published tomorrow, but in today's speech Lagarde gave a hint of what it is likely to include.
The economic risks of leaving are firmly to the downside.
Being part of the EU has greatly aided the transformation of the UK into a dynamic and vibrant economy. Membership of the EU has made the UK a richer country, but it has also made it a more diverse, more exciting, and more creative country.
- Christine Lagarde, International Monetary Fund
She also pushed back against the rising tide of support for "closed borders and economic nationalism", saying it presented a "serious challenge to the European project".
In the context of the EU referendum, Lagarde said: "I have always admired the UK for its openness to other nationalities and foreign cultures, and I find it hard to believe that attitudes have changed in such a short time.
"The UK has benefited from the many contributions of talented and hard-working migrants from all over the world, including the EU, while providing record-high levels of employment for all its residents".
However, the IMF chief, who has earned the scorn of Brexit campaigners for her interventions in the campaign, added: "Too many Europeans are worried about their cultural identity, their security, their jobs, incomes, and living standards."
Largarde said the EU referendum was one of three big challenges which "jeopardised" the immense gains the EU project has helped to achieve, along with the legacy of the Eurozone crisis and the refugee crisis.