1&1 Mobilfunk, a subsidiary of German telecoms company 1&1, has signaled its intentions to file a complaint against Vodafone for obstructing its 5G rollout.

The operator is filing its grievance with the Federal Cartel Office (Bundeskartellamt) over what it says have been 'ongoing obstacles to the rollout of its 5G mobile network resulting from actions by Vodafone’.

More specifically it's Vodafone's tower unit, Vantage Towers, that has been blamed.

1&1 holds the operator responsible for its delayed 5G rollout, after the two companies penned an agreement in 2021 for the shared use of 3,800 existing antenna sites for the new 1&1 network.

This agreement defined expansion targets for last year, but 1&1 says these targets were missed 'almost completely,' noting that by the end of last year, it only had a total of five 5G antenna sites, when around 1,000 sites were expected by the start of 2023.

1&1 goes on to say that Vodafone is planning and developing the shared use of Vantage Towers antenna sites by other network operators in Germany.

The operator emphasized its complaint further by noting that Vodafone had 1,600 5G antenna sites based on Vantage Towers infrastructure at the end of 2022, compared with its total of five.

To add to 1&1's problems, Vodafone has told the operator that there will be delays once again and that the new rollout plan will not be fulfilled either, with expansion targets planned for the first quarters of 2023 expected to be missed by a wide margin.

1&1 said it doesn't expect Vodafone's 'preferential treatment' of Vantage Towers' roll-out activities to end anytime soon.

"1&1 is doing everything possible to construct its new mobile network as quickly as possible," said the company in a statement. "The renewed delay in the provision of antenna sites by Vantage Towers may have an impact on the launch of mobile services on the 1&1 network planned for Q3 2023, in particular, because the technical certification processes required for this partly presuppose a certain minimum number of antenna sites. 1&1 is reviewing the schedule for further network rollout. A possible slight delay in the launch of the network would not have any noteworthy financial impact."

Vodafone sold off some of its Vantage Towers unit in November of last year, creating a new joint venture with KKR and Global Infrastructure Partners (GIP) in the process.