The Office of Fair Trading has referred the merger between AG Barr and Britvic to the Competition Commission.
The Competition Commission will investigate concerns that competition will be reduced between certain brands produced by the two companies, with Coca-Cola Enterprises the third of the three main companies working in the UK sector.
The acquisition, according to the OFT, raised concerns around competitive restraint over the IRN BRU and Orangina brands.
Amelia Fletcher, chief economist at the OFT Said that £9 billion was spent by UK consumers on soft drinks each year.
"This merger will see the UK market reduce from three to two main players. Our investigation has identified competition concerns relating to this deal with respect to Barr's IRN BRU and Orangina brands which could lead to higher prices for consumers," she added.
"'In addition, we could not rule out the possibility of further competition concerns arising from combining the overall Britvic portfolio of soft drinks with the entire Barr portfolio. We are therefore referring the merger to the Competition Commission for an in-depth investigation."
Barr produces Orangina, KA and Rubicon as well as IRN BRU, while Britvic owns Robinson's, Fruit Shoot, Tango and Pepsi.