Organisers of this summer's music festivals were urged to warn revellers about the dangers of so-called "legal highs".
Minister for Crime Prevention James Brokenshire wrote to festival organisers to help spread the message that what is marketed as a "safe" drug could be highly dangerous.
He said: "During the festival season we know that people may be tempted to try potentially dangerous new drugs, particularly when they are advertised as 'legal' or 'herbal'.
"That is why we are asking festival organisers and police to work with us to send out the message that these substances may not be safe and could contain illegal drugs.
"We are going to change our drug laws so we can respond quickly to emerging substances by introducing a temporary ban while we seek full scientific advice."
Some drugs previously sold as "legal highs" were banned, including mephedrone, now a Class B drug.
Another drug, naphyrone, is branded as NRG1 and sold as "plant food" or "bath salts", yet could contain one or more illegal drugs, the Home Office said.
The Government said it will not permanently ban a substance without receiving full advice from the Advisory Council on the Misuse of Drugs.
In the letter to festival organisers, Mr Brokenshire said: "As part of your preparations for this year's event I ask you to review the measures you have put in place to ensure that your festival is as safe an environment as possible, to help protect the public, especially young people from the potential harms and risks of all drugs."
Melvin Benn, managing director of Festival Republic, which stages the Latitude, Big Chill and Reading and Leeds Festivals, said he welcomed the Government's advice.
He said: "I can confirm that we do not allow legal high traders to trade at any Festival Republic festival and fully support the minister's view."
Mr Brokenshire said anyone wanting information on any kind of drugs should visit the Frank website at http://www.talktofrank.com or call their confidential helpline on 0800 77 66 00.
The letters were also sent to local authorities and police forces in areas hosting summer festivals.