The UK and US have signed a data access agreement to share social media and phone information to tackle major crimes, including terrorism.
The new agreement will come into force in October and will allow either nation to immediately access phone and social media data to help in major investigations, Britain's Home Office said.
The Data Access Agreement (DAA) will be the first of its kind, allowing each country’s investigators to gain better access to vital data to combat serious crime.
It will allow companies under US jurisdiction to share information which under American law they are not presently allowed to do.
"The DAA will transform the ability of UK law enforcement to promptly and efficiently access data that is vital to helping keep people safe," the Home Office said.
"When a UK law enforcement agency is trying to prevent, detect, investigate or prosecute a serious crime, the UK law allows them to seek data relevant to the particular crime. In the case of data held by telecommunications operators, this could include information such as pictures or messages."
Many of the popular telecommunications services, such as social media platforms and messaging services, operate within US jurisdiction, the Home Office said.
"Unfortunately, US law prohibits these companies from being able to share certain data in response to a request made directly by a foreign government. This means that data which might be essential to an investigation cannot be obtained.
"Whilst mechanisms such as ‘mutual legal assistance’ do allow government-to-government requests to be made for data, this process is typically very slow, often taking many months to complete.
"This can hamper critical investigations and prevent police or security services from building a picture of an investigation faster. In many cases, the person under investigation may continue to offend whilst the request is being processed, leading to more harm and more victims."
The DAA will provide relevant UK and US public authorities with timely, efficient and lawful cross-border access to data for the purpose of preventing, detecting, investigating and prosecuting the most serious crime, the Home Office said.
"It will ensure criminals cannot hide their data behind jurisdictional barriers to conceal their criminal activities."
The UK has also passed new legislation to provide the UK’s Investigatory Powers Commissioner’s Office with a statutory remit to oversee the UK’s use of the DAA.