The communications watchdog has launched an investigation into the business parcel delivery sector over competition concerns.

Ofcom said the probe would determine whether arrangements between companies was ultimately breaching EU law.

It said the investigation would look into “suspected market sharing and/or customer allocation arrangements between operators in the business parcel delivery sector in the UK and/or European Union.”

Those arrangements will be scrutinised over whether they prevented, restricted or distorted competition in the UK or EU.

A spokesman for Ofcom refused to outline which firms were being investigated.

The watchdog said the investigation was at an “early stage”, and stressed it had not yet concluded whether competition law had been breached.

The notice comes just one week after Ofcom fined Royal Mail £50 million.

The company was accused of abusing its dominant position by discriminating against its only major competitor for delivering letters, Whistl.

The penalty was the result of an investigation into a complaint lodged by Whistl, one of Royal Mail’s wholesale customers, following changes made to its wholesale customers’ contracts in 2014, including price increases.

The price rises meant that any of Royal Mail’s wholesale customers seeking to compete with it by delivering letters in some parts of the country, as Whistl was, would have to pay higher prices in the remaining areas – where it used Royal Mail for delivery.

Following notification of these new prices, Whistl suspended plans to extend delivery services to new parts of the UK.

Royal Mail said last week that it plans to appeal against Ofcom’s decision, claiming its price changes were “never implemented or paid”.