More must be done to raise awareness of the dangerous effects of laughing gas, councils have warned.
The Local Government Association (LGA) said it was "deeply disturbed" that nitrous oxide - which can result in a loss of blood pressure, fainting and even heart attacks - is still viewed as a safe legal high.
On a single Saturday night, one London council confiscated more than 1,200 canisters of laughing gas, while other local authorities are seizing "hauls" of the chemical, according to the Local Government Association.
Hackney Council in east London said that it took the small metal containers outside the pubs and clubs in Shoreditch on a Saturday night last month.
Officials in Norfolk, Hertfordshire and Thames Valley have reported increasing numbers of cannisters being found.
Prince William smiled and joked with colleagues as he posed for a group photo ahead of his final shift with the East Anglian Air Ambulance.
Opportunities were missed to prevent two teenage British Muslims being radicalised before they were killed fighting in Syria.
Charlie Gard will "inevitably" die shortly after being moved to a hospice and having life-support treatment withdrawn.