Its survey of 953 investors showed the rise in optimism was led by Germany, where the assessment of current conditions hit a record high in June.

Sentix said Europe's largest economy had driven the upturn in investor sentiment, helping the economy and the wider bloc to "boom".

Manfred Huebner, managing director at Sentix, said: "The situation in the Eurozone is getting better and better. For the sixth time in a row. Expectations remain positive."

By contrast, Sentix said sentiment towards the US was "cooling", with expectations turning negative for the first time since March 2016.

"The US economy is therefore cooling off, even if the all-time highs on the stock market convey differently," said Mr Huebner.

It came as separate eurozone data showed retail sales edged up in April, marking the fourth consecutive monthly rise.