The bus company Metroline has "signalled its intention" to withdraw its 84 route in its entirety from early April.
Hertfordshire County Council, who partly fund the route, said they are "still awaiting an official cancellation" from Metroline.
HCC added they are in discussion with other bus operators to see which elements of the 84 service they could potentially take on commercially.
Route 84 currently calls at the following stops: St Albans - Cell Barnes - London Colney - South Mimms - Potters Bar - New Barnet.
A London Colney resident posted an angry reaction to the news on the neighbourhood app Nextdoor.
They said: "This is outrageous. It's the only route running from St Albans, through London Colney to Potters Bar and New Barnet.
"It's a vital lifeline for many people, particularly the elderly who regularly use it to get into Potters Bar or to the shops at Colney fields.
"The removal of this route would leave many people stranded, including many who work in Colney Fields or St Albans."
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