The announcement was leaked online early on Wednesday, with the ACCC saying that it would issue a full explanation in due course

Australia’s anti-monopoly watchdog has blocked the proposed merger between Vodafone Australia and TPG Telecom. The pair had been set for a A$15 billion (£8.4 billion) merger but The Australian Competition and Consumer Commission blocked the deal earlier today. 

"The ACCC has decided to oppose the proposed merger between TPG Telecom Limited (ASX: TPM) and Vodafone Hutchison Australia Pty Ltd (ASX:HTA). This information was inadvertently published online on our mergers register briefly this afternoon. We intend to publish a further media release shortly," a statement from the ACCC read. 

The pair had hoped that the merger would allow the newly formed entity to access cost saving synergies and be able to leverage enhanced economy of scale in the Australian fixed line and mobile markets. 

Vodafone Hutchison Australia (VHA) is ostensibly a mobile network operator, while TPG Telecom provides fixed line broadband services. The ACCC is believed to have concerns that the proposed merger would have reduced competition for consumers in Australia. 

Neither Vodafone nor TPG have yet commented on the rejection of the deal.