A mobile network is reportedly depositing £1 million in cash a week at London Post Offices - and no one knows why

Lycamobile, a mobile virtual network operator (MVNO) with sales of over £1.1 billion ($1.6 billion) per year is reportedly depositing up to £1 million ($1.5 million) in cash per week at various Post Office branches around London, according to BuzzFeed News.

BuzzFeed News uncovered the practice as part of a five-month investigation, which was described as "deeply suspicious" by experts.

Twice every day, employees of Lycamobile collect cash in bags - some of which contain up to £260,000 ($395,000) - and drive in unmarked people carriers to Post Office branches where the money is deposited into the company's Santander account, according to the report.

These payments reportedly total up to around £1 million ($1.5 million) per week. Over the past three years, Lycamobile has deposited over £156 million ($236 million) in this way, BuzzFeed News said.

Business Insider has reached out to Lycamobile for comment.

While the practice is not overtly illegal, it does raise questions about why Lycamobile does not transfer money through the usual channels. BuzzFeed News notes that the company employs G4S, the security firm, to move the rest of its money and its just this cash which gets special - and off-the-record - treatment.

BuzzFeed News interviewed Post Office employees, who wished to remain anonymous, about Lycamobile's deposits. Many of those interviewed claimed that while other company's do deposit cash in this way, it is usually only amounts of around £26,000 ($40,000). The Post Office have flagged up the issue in the past causing Santander to limit daily deposits for Lycamobile to £120,000 ($180,000).

The findings have also placed scrutiny on the Conservative Party, which has taken more than £1.3 million ($1.9 million) in donations from Lycamobile since 2010. Several Labour MPs have called for the party to look at who it accepts donations from.

The founder of Lycamobile, Subaskaran Elijah, also has close personal ties to the Conservative Party, donating over £200,000 ($300,000) for a bust of Margaret Thatcher in February 2015. He regularly meets with Prime Minister David Cameron.

Additionally, Lycamobile is under investigation from the Sri Lankian authorities for connections to corruption. BuzzFeed News notes that there is no obvious connection between the cash deposits and the investigation, however.

The reason for the off-the-record cash deposits is unknown and while there is no obvious wrongdoing it does raise questions about Lycamobile's practices.

Read the full BuzzFeed News report here »