The phrase "a report has warned" is correct and usable in written English.
It can be used when referencing a warning or caution provided by a report, typically in a formal or journalistic context.
Example: "According to the latest findings, a report has warned that climate change could lead to severe weather patterns in the coming decades."
Alternatives: "a report has cautioned" or "a report has indicated".
Huge mineral deposits in Uganda's Karamoja region, expected to regenerate the conflict-ravaged area, could instead further deepen the suffering of people living there, a report has warned.
Half of nurses are working through breaks or beyond their shift, revealing a health service under severe strain, a report has warned.
The HS2 high-speed rail project could nearly double in cost to £80bn and should be dropped, a report has warned.
Weaknesses in Britain's border security may allow terrorists to get the guns they need to attack London, a report has warned.
Trouble is brewing for the traditional British cuppa, a report has warned, with sales falling by more than 6% over the past five years.
Land degradation is costing the world as much as $10.6tn every year, equivalent to 17% of global gross domestic product, a report has warned.
Canada's attempt to act on climate change is being undermined by $3.3bn in government subsidies flowing to oil and gas producers in the country a year, a new report has warned.
The future of 5.5 million children living in Syria and neighbouring countries hangs in the balance as violence, collapsing health and education services, severe psychological distress and impoverishment combine to scar a generation, a UN report has warned.
Australia is one of just four nations not on track to meet emissions reduction promises, a UN report has warned, while a US-based research firm has poured scorn on Tony Abbott's insistence that coal is "good for humanity".
A United Nations report has warned of a $460 million shortfall in aid for Yugoslavia and stressed the need for urgent international action to help the Balkan country after the fall of Slobodan Milosevic.
NHS non-emergency helplines are not sensitive enough to identify when some children have a potentially fatal illnesses, including sepsis, a new report has warned.
