Stroke victims and their families should call 999 as soon as just one symptom appears, England's top doctor has urged.
Health officials said widespread confusion about deadly symptoms was leaving people waiting almost 90 minutes to call emergency services.
It comes as polling today shows that the majority of people believe they should only call 999 if someone has multiple symptoms.
Medical professionals say tens of thousands of people could be diagnosed more quickly, with many lives saved and devastating disabilities prevented, if the crucial call was made sooner.
The NHS will today launch the first major update to its "Act FAST" campaign in 15 years.
The public will be urged to call 999 if anyone experiences at least one of three common symptoms: struggling to smile (Face) raising an arm (Arm) or slurring their words (Speech).
Professor Sir Stephen Powis called on the public to call 999 even if the first sign of a stroke doesn't seem like an emergency, saying swift action "could help save and protect many more lives".
The new campaign will stress that just one sign is enough to constitute a medical emergency, requiring immediate action.
It comes as a national audit of NHS data found that the average time between first symptom and making a 999 call was 88 minutes.
Around 100,000 people have a stroke each year in the UK, which occurs when the blood supply to part of the brain is cut off.
Without prompt treatment a stroke can result in death or long-term disabilities such as paralysis, memory loss and communication problems.
Every 20-minute delay is associated with an extra percentage in loss of function, research shows.
Professor Sir Stephen Powis said: "These figures highlight very clearly that we must do more to support people to recognise the symptoms of stroke in themselves and others and take action to call 999 at the earliest opportunity.
"Stroke symptoms can be less obvious or dramatic than you might expect, but even if it doesn't seem like it, any sign of stroke is always an emergency and it's vital you call 999 immediately.
He said: "This campaign is so important - greater awareness of the need to act fast and dial 999 could help save and protect many more lives, as we know that earlier recognition of symptoms and immediate action to call 999 can enable faster access to specialist treatment and the best chance of reducing long-term effects of a stroke."
Health officials said survival from strokes has improved, thanks to advances in NHS care.
But strokes remain the fourth-greatest single cause of death in the UK.
There are 38,000 stroke-related deaths each year, down from 66,000 in 2001.
The data on how long patients took to call 999 came from analysis of calls about 41,327 patients in 2023/24.
The audit by the Sentinel Stroke National Audit Programme at King's College London, is the first time such data has been published.
It came as polling of 2,001 adults in England found that 57 per cent of respondents believed you should have two or three symptoms of a stroke before calling 999.
Just 38 per cent of those polled thought they should act on just one sign.
The NHS campaign will launch a new TV advertisement showing examples of symptoms.
In one case a woman can be seen struggling to smile while watching TV (Face), while in another a decorator is unable to lift their paint roller (Arm), while a grandmother struggles to read their grandchild a bedtime story (Speech).
The advertisements will run across TV, TV on demand and radio in England until mid-December.
As part of the campaign launch, a film has also been released which features stroke survivors listening back to audio recordings of the real 999 calls that saved their lives.
A stroke can happen to anyone at any age, but those at increased risk include people aged over 50 years old, people from a Black or South Asian background, or those living with existing conditions such as high blood pressure, diabetes or sickle cell disease.
Dr David Hargroves, NHS national clinical director for stroke and consultant stroke physician, said: "When someone has a stroke, it's estimated they may lose around two million brain cells a minute, which is why rapid diagnosis and treatment is critical - the first sign of a stroke might not seem like much, but face or arm or speech, at the first sign it's time to call 999.
"Thanks to greater awareness of the symptoms and advances in NHS care, more people are now surviving a stroke than ever before, but there is much more to do to help save lives and reduce the long-term impact of strokes. Acting FAST remains vital - whether it is a friend, loved one or even a passerby, dialling 999 quickly saves lives."
Public health minister Andrew Gwynne said: "It is important to treat a stroke quickly and raising awareness of symptoms is vital to saving lives.
"It is not just about recognising when a stroke is happening - we know that many of the causes of strokes are preventable, and this government is taking action to tackle the biggest killers such as heart disease and stroke.
"The NHS Health Check programme aims to prevent cardiovascular disease, including stroke, in people aged 40-74 years through assessing risk factors such as blood pressure and referring people to behavioural support and clinical treatment to reduce their risk.
"Each year the programme engages over 1.3 million people and prevents around 500 heart attacks and strokes a year.
"We are currently developing a new digital NHS Health Check enabling people to complete this life saving check in their own home."
Juliet Bouverie, chief executive of the Stroke Association, said surviving a stroke is just the start of a "long and traumatic battle".
She said: "Mums, dads, grandparents, young people, even children can be stroke survivors, and the impact of stroke on them and their loved ones can be catastrophic.
"This new NHS campaign is so important to help raise awareness that a stroke is always a medical emergency. If you spot any of the three common signs of a stroke in someone, the first thing you should do is call 999. The quicker stroke treatments are given, the better. As we say, 'time is brain', so it's important to recognise any of the signs of a stroke and act immediately. Acting FAST is vital for stroke survival and to help improve the journey to recovery."
Brian Turner, a celebrity chef, aged 78, suffered a stroke in 2022.
He said: "I'm so lucky my agent Louise recognised that I was experiencing a sign of a stroke. She noticed that I couldn't speak properly and immediately called 999, ensuring that I could get lifesaving treatment from the NHS. Without her, I wouldn't be where I am now. I'm proudly supporting NHS England in urging the public to act FAST and call 999 at the first sign of a stroke."