The 189 service has been erratic since its frequency was changed from every 10 minutes to every 15 minutes, passengers claim.
Operator Arriva has apologised for the issue, which it says has been caused by heavy roadworks around Normanton, where the service stops, rather than the timetable change.
Speaking in response to a passenger who complained about the service at a transport meeting on Thursday, Arriva Yorkshire's head of commercial admitted the 189 was "not up to our usual standards".
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Dwayne Wells said: "It's probably coincidental that the issues have started since the timetable change.
"We're experiencing a number of roadworks, particularly around the Normanton area, which is severely affecting that service and there have been delays of up to 45 minutes at times on that service.
"We are monitoring it and it is getting better as the roadworks are subsiding, but unfortunately we are in that position."
Mr Wells said Arriva was working with Wakefield Council to try to stagger roadworks in future, so as to avoid having several sets of repairs taking place across one single bus route.
He added: "We are aware of the delays and we do apologise for it.
"It's something that's out of our control but we are working with the council to try to mitigate it."
Mr Wells later extended his apologies to all bus passengers across the Wakefield district, as he acknowledged there had been recent problems across the network.
The operator is making sweeping and controversial changes to timetables on October 25, including axing three different services.
The changes have been forced by a serious shortage of drivers, in part due to a recent exodus of staff to the HGV industry, where wages are generally higher.
Mr Wells said the shortage, "is forcing us to cancel some services."
He explained: "Normally we'd have spare drivers to cover any sickness on the day that may emerge, but we've been stepping those drivers up to cover vacant duties.
"That means we're less able to react to absences that may occur on the day.
"So I apologise to customers and thank them for bearing with us.
"We have been prioritising hourly services over ones that are more frequent."
Mr Wells said Arriva was carrying out an "intensive" recruitment campaign to address the shortage.
He indicated that there were sufficient number of applicants for the vacancies, but said there was a time lag of "about 16 weeks" to interview, appoint and then train drivers up.
Local Democracy Reporting Service