The spokesperson said the ManaBus and Naked Bus fleets had been sold to Ritchies Transport Holdings as part of the decision to exit the space.
"As of 15 July, ManaBus.com and nakedbus.com bus services will cease operation and tickets will no longer be available to purchase," the spokeswoman said.
Customers who bought tickets in advance have already been offered full refunds via email.
"Fullers is working closely with its staff, partners and customers throughout this process to support them through this transition," she said.
ManaBus was first launched as a budget travel option in 2014 by Scottish transport entrepreneur Brian Souter, adding to a portfolio that included Auckland urban bus companies Howick and Eastern Buses, the Wellington-based bus service Mana Coach Services and Waiheke Bus Company, as well as the Auckland Fullers Group ferries and the 360 Discovery cruises.
In May 2015, Souter's company acquired rival Naked Bus in a bid to expand the company's footprint across the South Island.
Read more: ManaBus.com buys Naked Bus for undisclosed sum as it looks south
At the time of the acquisition of NakedBus, Manabus said the combined entities across the entire portfolio transported more than 13 million customers a year and employed 670 people.