Companies using line rental services from BT Business are set to be hit by a significant price rise following the unveiling of new charges from the operator.

The company wrote to its customers over the weekend to inform them that from August 1, the cost of their line rental increase by an average of 5.5%, with the prices of some of its broadband packages and products also set to change.

The rise may fall foul of new regulations introduced by industry watchdog Ofcom earlier this year aimed at protecting small businesses from mid-contract price hikes. The new guidelines, introduced in January, state that any companies taking out new landline, broadband or mobile contracts should be allowed to exit them without penalty if their provider increases the monthly subscription price agreed at the point of sale.

BT Business currently provides broadband and phone line services for businesses, including access to the company’s superfast Infinity network, with deals currently starting at £45 a month, as well as allowing access to BT’s five million Wi-Fi hotspots across the country.

The firm counts around 60% of Britain’s small and medium businesses amongst its 900,000 customers across the UK. A separate arm of the BT family since its spin-off in October 2013, the company is responsible for many key BT products, including the 999 service, directory enquiries, and the company’s payphone network.

Earlier this month, it announced the launch of BT One Phone, a new cloud-based mobile offering for businesses, which it says will help cut costs and provide better and more reliable calls for SMEs.