It is unusual for a senior figure at the Bank to be so forthright on market movements.
The US president-elect comes into office with a strong economy, but investors hope for more and current highs may be difficult to sustain.
Investors expect artificial intelligence to unleash a new wave of growth.
Investors have been cheered by hopes that the US central bank's campaign of raising interest rates is over.
The Dow Jones share index closed below 30,000 at its lowest level in more than a year.
UK shares slide after more signs of waning consumer confidence trigger steep falls in US markets.
The sell-off comes as worries intensify over how the rising cost of borrowing will affect economic growth.
Major US stock indexes took a slide in April, with the tech-heavy Nasdaq seeing its worst month since 2008.
The falls came as the US accused Russia of preparing fabrications to justify an invasion.
