Bundeskartellamt, Germany’s anti-trust regulator, has asked the EU to take a lead role in scrutinising Telefonica’s €8.6 billion takeover of E-Plus, the German business unit of KPN.

According to a Reuters report, Bundeskartellamt says the deal – which would create Germany’s largest mobile operator by customers, and reduce the number of network players in the market from four to three – requires “in-depth examination”.

Under the original regulatory timetable, the European Commission was scheduled to decide on 6 December on whether or not to approve the deal.

Another EC option is to launch a detailed investigation of the tie-up.

The decision is now expected on 20 December, giving more time for the commission to consider the request made by Germany’s antitrust regulator.

The general view among analysts, as well as Telefonica and KPN, is that an investigation will be the preferred course. Both operators have said they don’t expect to close the deal until the summer.

Bundeskartellamt says it has the backing of the country’s federal ministry for economic affairs in its desire to lead the investigation.

“The merger exclusively affects the German mobile communications markets,” said the anti-trust regulator in statement quoted by Reuters. “A referral of the case to the Bundeskartellamt would thus be the right approach.”

Antitrust lawyers told Reuters that Telefonica will try and win approval for the deal by pledging to divest spectrum and give MVNOs access to the combined metwork.

The European Commission recently decided to launch a further investigation into the proposed €850 million bid by Hutchison Whampoa for Telefonica’s O2 unit in Ireland, which would also see the number of mobile network operators in the country trimmed from four to three.

Brussels is not impervious to the idea of consolidation, however, giving its blessing to Hutchison’s takeover of Orange Austria last year.