The head of the International Monetary Fund has made an impassioned plea for the UK to vote to stay in the EU, arguing that membership of the bloc has made the economy stronger and the country more diverse and creative.

Christine Lagarde used a speech in Vienna to warn of a worrying rise in economic nationalism that threatened the union and urged policymakers to do more to reduce the inequality that made some Europeans “feel left behind”.

With less than a week to go until the referendum, Lagarde repeated her assertion that it made economic sense to stay in the EU and rebuffed suggestions that migration had hurt the jobs market.

In her latest intervention, the French-born IMF managing director also pointed to Britain’s track record on migration. Noting the role of refugee and migration issues in the referendum, she said: “I have always admired the United Kingdom for it openness to other nationalities and foreign cultures, and I find it hard to believe that attitudes have changed in such a short time. But this is for British voters to decide, and their decision clearly depends on many factors.”

Lagarde repeated the IMF’s view that the economic risks of Brexit were “firmly to the downside”. She said there was a clear case of how the UK had benefited from more jobs and income as a result of increased trade in the EU and greater investment.

She added: “Being part of the EU has greatly aided the transformation of the UK into a dynamic and vibrant economy. 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.”

“As in all countries, there are people who are struggling in this new environment, but for the majority of citizens, this has been a great success story.”

On the wider EU, Lagarde built on her recent remarks about growing protectionism and the rise of nationalist parties. “Too many Europeans are worried about their cultural identity, their security, their jobs, incomes, and living standards. And too many of them are led to believe that things would be better if only Europe returned to closed borders and economic nationalism,” she said in the speech entitled Unity in diversity: the case for Europe.

“This is a serious challenge for the European project. It is high time to confront this negative vision with a new perspective for those citizens who feel left behind.”

Previous IMF interventions in the 23 June referendum have drawn an angry response from leave campaigners who have said the organisation should not interfere in the UK’s democratic process. The leave camp has also attacked its record on economic forecasting.

The IMF said last month Brexit could trigger a stock market crash and a steep fall in house prices.

Lagarde’s latest comments on the issuet echoed the Bank of England’s warning on Thursday that leaving the EU would risk pushing the pound sharply lower and sending shockwaves through the global economy.