Pepsi Bottling Group has rejected a takeover approach by soft drinks manufacturer PepsiCo.

The bottler said PepsiCo’s approach was “grossly inadequate” and not in the best interests of the company.

PepsiCo offered to buy both Pepsi Bottling Group and PepsiAmericas for $6bn last month, valuing both companies at a 17% premium on their share prices.

But in a letter to PepsiCo chairman Indra Nooyi, Pepsi Bottling Group chief executive Eric Foss said the offer had “opportunistic timing”, was of “inadequate value”, and had “understated synergies” between the companies.

“Pepsi Bottling Group values its longstanding relationship with PepsiCo but the board will not agree to a proposal [that] does not reflect the true value of Pepsi Bottling Group,” Foss said.

He added: “We remain confident that Pepsi Bottling Group’s continuing efforts to strengthen its brand portfolio, further improve its performance through operational excellence, and capitalise on geographic growth opportunities position Pepsi Bottling Group to create substantial value well into the future.”