America's National Security Agency has collected almost 200 million text messages a day from across the globe according to the latest leak from former US spy Edward Snowden.
The claims are made by Channel 4 News and the Guardian newspaper who have seen a classified April 2011 presentation which discusses Dishfire, a database that collects nearly 200 million texts every day from around the world.
Dishfire traces people when they take their mobile phone abroad by capturing the welcome text message that is triggered by your arrival overseas.
This tells agents where you were and when you got there.
It is claimed the texts help the NSA to track people's whereabouts, their contacts, their banking details and their movements if they travelled from country to country.
Under US law, the American spies had to delete the data for its own citizens but texts coming to and from international mobile phones - were fair game and could be spied upon at will.
Reports suggest British spies can access the system to access information without receiving formal permission or warrant.
Communications giant Vodafone told Channel 4 News they were "shocked and surprised" by this potential for exploitation.
"What you're describing sounds concerning to us because the regime that we are required to comply with is very clear and we will only disclose information to governments where we are legally compelled to do so, won't go beyond the law and comply with due process," Stephen Deadman, group privacy officer and head of legal for privacy, security and content standards at Vodafone Group, told Channel 4 News.
"But what you're describing is something that sounds as if that's been circumvented. And for us as a business this is anathema because our whole business is founded on protecting privacy as a fundamental imperative.
"We're going to be contacting the (UK) Government and are going to be challenging them on this. From our perspective, the law is there to protect our customers and it doesn't sound as if that is what is necessarily happening."
The NSA has stated that Dishfire does exist and that it lawfully collects SMS data. It also stated that privacy protections are in place for US citizens.
Edward Snowden, is a former NSA contractor, who is now hiding in Russia after leaking classified government documents.
On British soil, spy agencies can only access text message data of specific targets with permission under the Regulation of Investigatory Powers Act (RIPA), and if they want to see the content of the message they must get a warrant from a secretary of state.
By contrast Dishfire collects data on everyone so by accessing the system, British spies can pull off information they wouldn't be entitled to under strict British laws.
Communications giant Vodafone told Channel 4 News they were "shocked and surprised" by this potential for exploitation.
"What you're describing sounds concerning to us because the regime that we are required to comply with is very clear and we will only disclose information to governments where we are legally compelled to do so, won't go beyond the law and comply with due process," Stephen Deadman, group privacy officer and head of legal for privacy, security and content standards at Vodafone Group, told Channel 4 News.
"But what you're describing is something that sounds as if that's been circumvented. And for us as a business this is anathema because our whole business is founded on protecting privacy as a fundamental imperative.
"We're going to be contacting the Government and are going to be challenging them on this. From our perspective, the law is there to protect our customers and it doesn't sound as if that is what is necessarily happening."
The NSA has stated that Dishfire does exist and that it lawfully collects SMS data. It also stated that privacy protections are in place for US citizens, according to Channel 4 News.
GCHQ said: "All of GCHQ's work is carried out in accordance with the strict legal and policy framework which ensures that our activities are authorised, necessary and proportionate and that there is rigorous oversight."
Edward Snowden is a former NSA contractor who is now hiding in Russia after leaking classified government documents.
