A variety of domestic and foreign smartphones are being accused of stealthily connecting to the Internet and eating into the data packages of users, China Central Television reports.

On July 1, the Shanghai Consumer Council filed two separate lawsuits against Guangdong Oppo Mobile Telecommunications Corp and Tianjin Samsung Telecom Technology Co, accusing them of infringing upon legal consumer rights.

The Shanghai authority set up a test, buying 20 smartphones, covering foreign brands like iPhone and Samsung, as well as domestic brands including Oppo, Huawei and Lenovo, while selecting ten data packages from different providers.

Results showed that iPhone stealthily consumed 80 MB in 120 hours, the highest in the group. Calculated based on China Mobile's offer for additional data of 15 yuan per 110MB, usage was equivalent to an extra bill of more than 60 yuan a month.

In another test, OPPO was found to have the highest number of pre-installed software, with 71. VIVO coming second with 58.

While OPPO also has the highest number of non-removable pre-installed software at 47, VIVO has the highest number of removable pre-installed software at around 33.

Meizu was found to have the lowest number of pre-installed software at 30, 10 of which are removable.

Samsung has 44 software pre-installed, none of which can be removed, making it second only to OPPO in this regard.

Pre-installed software on iPhone and domestic brand Gionee cannot be uninstalled, either.

Non-removable pre-installed software occupies storage space on a phone and thus infringes upon consumer rights, the Shanghai authority claims.

Customer complaints regarding smartphones have been on the rise across Shanghai since 2012 and have been topping the list of product complaints for three consecutive years, according to the authority.

Law experts say smartphone users should have the right to decide whether they want to keep installed software and access the internet or not, especially when such services incur fees.