Professor Hugh Markus, from the Centre for Clinical Neuroscience at St George's, University of London, said three different studies had put the UK at the bottom among several other Western European countries.
Writing in the British Medical Journal (BMJ), he called for medical professionals and the public to start seeing stroke as something that needs emergency action.
He also cited a "severe shortage" of specialists trained in acute stroke care and said that this would take years to turn around, despite Government efforts.
An estimated 150,000 people in the UK suffer a stroke each year, according to the Stroke Association.
Stroke is the third most common cause of death in the UK, accounting for more than 60,000 deaths a year.
It is also the single most common cause of severe disability. More than 250,000 people live with disabilities caused by stroke.Prof Markus detailed several interventions where the UK lags behind, such as brain computed tomography (a CT brain scan) - which is performed on admission to A&E in many European countries, he said.
But in the UK, many units "struggle" to provide it within 24 hours, he added.
This was despite research showing that it was the most cost-effective strategy and could help tailor care.
Joe Korner, director of communications at The Stroke Association, said: "For many years The Stroke Association has been concerned about the UK's poor record in stroke care compared to other countries.
"That is why we have been campaigning hard to try and improve stroke services nationwide.