The word 'warns' is correct and usable in written English.
You can use it when you are expressing a warning to someone. For example: "The doctor warns that smoking is bad for your health."
Harper, who was steering an immigration bill through the Commons that warns employers of their duty to check the status of employees, notified David Cameron on Friday, when his resignation was accepted "with regret".
It reads: "Voting for UKIP is like writing a 'suicide note' which will 'not be forgiven' if it denies Britain the chance to vote on whether to remain a member of the EU, Iain Duncan Smith warns today.
A presentation compiled by Australians for Animals and sent to the environment minister warns that large numbers of dugongs are being stranded on beaches and that dredged spoil is wiping out vast tracts of seagrass.
The D-notice committee opens a bleary eye, warns editors off, and goes back to sleep.
He warns that the ability of British people to travel as freely as they do now, and to work and buy homes in other EU countries, would also be lost, and that UK businesses would suddenly face new problems, as the country would no longer be able to influence the rules of the internal market.
Davide Pugliese, the chef who served up our best meal at the excellent Brandywine Bay restaurant on Tortola, warns that tropical fish poisoning, or ciguatera, can be caught from predatory fish caught around local reefs.
A paper in the Lancet Infectious Diseases medical journal models the response in Montserrado, Liberia, against the spread of the virus and warns that current efforts will not bring the outbreak under control.
It is understood the formal complaint warns that the Gulf state, which is a member of the ILO, "is in serious breach of its legal obligations" under the convention concerning forced labour, which it ratified more than 30 years ago.
Related: Election 2015 live: Clegg warns of second election before Christmas without Lib Dems in coalition "I tell you folks," Boris confided in his audience.
The Royal College of Nursing (RCN) has praised the skills of foreign nurses who come to the UK, but warns that continually recruiting from abroad is expensive – and unfair on thousands of young Britons who would be keen on a career in the health service but are not given the opportunities.
He sees the similarities between Scotland and Catalonia but also warns against exaggerating them.
