The Aberystwyth depot for Arriva Buses Wales will close today, alongside those in New Quay, Lampeter and Dolgellau.
The company says the period of instability regarding public transport funding - together with spiralling fuel costs, has put unsustainable financial pressure on their Aberystwyth operations.
Ceredigion MP Mark Williams has launched a petition, calling for a new operator to be found for six bus services, which Arriva announced would be cancelled from December.
Arriva Buses Wales said yesterday that Services 20, 40, 40C, 50, 585 and X94 will stop, its Aberystwyth depot, and New Quay, Lampeter and Dolgellau outstations will close, with up to 46 jobs potentially lost.
It said "spiralling fuel costs has resulted in an unsustainable financial pressure."
Local MP Mark Williams reacted on Twitter: "I am absolutely appalled by Arriva's decision to axe half a dozen bus services in Ceredigion and isolate many of my constituents."
Arriva buses have cited "spiralling fuel costs" and "unsustainable financial pressure" as part of the reasons for proposing the closure of various sites across Wales.
The Unite union has raised concerns over proposals by Arriva buses to cut up to 46 jobs across sites in Wales.
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