Germany's competition regulator will investigate whether Vodafone's German Vantage Towers unit blocked rival 1&1's 5G network rollout.

The Bundeskartellamt (Federal Cartel Office), will look into complaints made by 1&1 earlier this year, to determine if Vodafone and/or Vantage violated German or EU competition laws by delaying allocating locations to the rival company.

"Powerful and dominant companies must not unfairly impede other companies. We will therefore scrutinize whether there are sound reasons for a delay in the provision of antenna locations for 1&1," Andreas Mundt, president of the Federal Cartel Office, said in a statement.

In February, 1&1 complained that it was facing 'ongoing obstacles to the rollout of its 5G mobile network resulting from actions by Vodafone’.

The two companies agreed in 2021 that the new 1&1 network could share 3,800 existing antenna sites. The agreement included expansion targets, with 1,000 sites due to be live by the end of 2022. In the event, 1&1 says the target was missed 'almost completely,' with a total of five 5G antenna sites up and running by the start of 2023.

In May, the operator said that its partners were now more cooperative, highlighting support from Telefónica in particular. A new rollout plan published in March promises 1,200 antenna masts by the end of 2023.

Vodafone told Reuters that it rejects the accusation it has blocked 1&1's 5G rollout.