Up to one in three NHS hospitals still permit smoking in their grounds, despite bosses calling for a ban since 2013.
A poll of NHS acute trusts in England by Public Health England (PHE) found 31 per cent still allow smoking in areas of hospital grounds.
However, it is banned by law in Northern Ireland and Scotland and a legal ban is set to be introduced in Wales by the end of this year.
But it is still not illegal to smoke in hospital grounds in England.
In 2013, the National Institute for Health and Care Excellence (Nice) said: "NHS hospitals in England should ban smoking on their premises and staff should be told not to help patients who want to smoke."
And in November 2016, PHE's chief executive Duncan Selbie wrote to the chief executive of every NHS Trust in England, calling for their personal commitment to work with PHE towards a "truly smokefree NHS".
In the latest survey of 145 NHS acute trusts, PHE said trusts were making "steady progress" towards becoming smokefree.
Some 69 per cent of NHS acute trusts in England (100) now ban smoking completely on their grounds but 31 per cent (45) have not yet enforced total smoking bans across hospital premises.
The NHS Five-Year Forward View included a commitment for all trusts to have fully smokefree sites by spring 2020.
Mr Selbie said: "One in four hospital beds are occupied by a smoker and most of them want to quit.
"Many patients or visitors will be going through difficult times but smoking remains England's biggest preventable killer and it is time for the NHS to stop smoking within its hospital grounds, everywhere.
Public health minister, Seema Kennedy, said: "No-one should have to walk past a cloud of smoke in order to enter or leave their local hospital, we must lead by example and I am determined to see a smoke-free NHS by 2020."
