[VIENNA] International Monetary Fund managing director Christine Lagarde warned the UK of the risks of leaving the European Union and said there was a clear economic argument for remaining part of the bloc.
EU membership has brought jobs and income gains to Britain and helped make the country a "dynamic and vibrant economy," MsLagarde said in the prepared text for a speech in Vienna on Friday.
European integration has lifted trade and investment and raised productivity and incomes, she said.
"We have already been on record that the economic risks of leaving are firmly to the downside," Ms Lagarde said. "There is, in my view, a clear case as to how the UK has benefited - and will continue to benefit - from its membership in the European Union."
In the UK referendum campaigns were suspended for a second day on Friday after the death of Labour lawmaker Jo Cox, an advocate for "Remain."
The IMF delayed by 24 hours the publication of a detailed report on the implications of Brexit.
Ms Lagarde's warning reiterates the message contained in an IMF report last month which warned Brexit could lead to a "protracted period of heightened uncertainty," triggering financial-market volatility and hurting economic output.
The fund also warned it could erode London's position as a financial center and cause "sharp" falls in house and equity prices.
Acknowledging that refugee and migration issues play an important role in the Brexit debate, Ms Lagarde urged British voters remain open to immigrants and the role they play in the economy and society.
"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," Ms Lagarde said.
"Membership in the EU has made the UK a richer economy, but it has also made it a more diverse, more exciting, and more creative country. 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."