Children's healthcare is being "increasingly compromised" as a result of staffing shortages across the UK's paediatric units, leading doctors have warned.
The Royal College of Paediatrics and Child Health (RCPCH) raised concerns that healthcare for children is "starting to move backwards".
The paediatric workforce across the UK is at "breaking point", the College said, after its new survey highlighted more than half of paediatric units are not meeting RCPCH-recommended staffing standards.
It said that to keep services running, consultants are increasingly providing unplanned cover in addition to performing their own roles.
And almost nine in 10 (89%) of clinical directors said they are concerned about how paediatric services will cope in the next six months, according to the survey of 93 paediatric and neonatal units.
The Rota Vacancies and Compliance Survey highlighted gaps across junior doctor rotas. Three in five "tier 1" rotas - which are made up of the most junior doctors - were not able to meet the RCPCH recommendation of 10 full-time staff.
And 77% of "tier 2" rotas - made up of more senior trainees - were not meeting the RCPCH quota.
As a result, many consultants are plugging rota gaps - with 38% of paediatric units claiming they have used consultants to fill junior doctor rota gaps in 2016 compared to 35% in 2015.
Dr Simon Clark, workforce officer at the RCPCH, said: "The paediatric workforce is at breaking point and children's healthcare is increasingly being compromised.
"There is no escaping the fact that an increase in junior and consultant posts is urgently needed, coupled with a radical re-design of services.
"The NHS was designed in the 1940s when paediatric care took second place to the care of adults. Children are not small adults and paediatricians are proud to have helped focus attention on their needs.
"The RCPCH wants to see children's healthcare move forward, not stand still, and now we fear things are starting to move backwards."
On the imposition of the new contract for junior doctors, Dr Clark added: "Since the imposition of the highly damaging junior doctor contract, we have evidence from the College's existing recruitment data that morale is at an all-time low.
"In a reversal of previous years' figures, junior doctors are choosing to move out of England; 100% of posts at junior trainee level were filled in Wales, Scotland and Northern Ireland compared to 93% in England."
Reacting to the poll, Dr Andrew Goddard, Royal College of Physicians registrar, said: "The situation our paediatric colleagues are in is worrying familiar.
"Physicians are also facing rota gaps, consultants acting down into trainee positions, inability to recruit to posts in key specialities due to a lack of trainees, and difficulties in covering day-to-day services.
"We're heading into an extremely difficult autumn."
A Department of Health spokeswoman said: "We're helping the NHS cope with increased demand by recruiting more staff, with 9,100 extra doctors and 11,200 more nurses on our wards since May 2010.
"Medicine remains an attractive career, and figures show that applicants for medical training programmes this year have matched previous years."