The shock rise has led to a head-on collision between Greenock-based McGill's and Paisley MSP George Adam who says there has been a public backlash.
The row centres on the introduction this week of a 10% hike on the cost of all weekly and monthly tickets for adults, students and children.
It is the third increase in a year.The company upped fares last January for the first time since taking over from Arriva Scotland West in March, 2012.
That triggered fury too.
Passengers in Foxbar complained a return ticket to Paisley Cross more than doubled from £1.50p to £3.10 while in September the firm introduced a second rise by increasing the price of four multi-journey tickets which affected one office executive who travels between Renfrew and Glasgow City Centre.
The Evening Times told yesterday how his four-week travel ticket had risen in price from £45.50 to £55 over the last 12 months.
He claimed: "It's beginning to look as if they are taking advantage of their monopoly which just isn' t right."
Bus bosses denied the claim and blamed several factors for a third price hike in just 12 months including rising labour and material costs and cutbacks in government subsidies for concessionary fares.
Mr Adam is calling on McGill's bosses to think again. The SNP politician said: "Having any extra expense after a busy festive period is always going to be unwelcome but for this to happen for a second year running is a real blow.
"Many of my constituents rely on buses to get to and from the town centre for shopping and work. Many people on low wages cannot afford to pay more for their transport.
"As McGill's is the main bus operator in our town, I would have hoped they would have paid more attention to this factor before increasing their prices yet again."
The Holyrood politician added: "I have been contacted by numerous constituents regarding this issue and have written to McGill's asking for an explanation why the decision was taken to increase fares once again, specifically at this time of year, while asking that in light of these complaints they look to reverse their fare increase."
The company isn't expected to scrap the rise.
A spokeswoman said senior management officials were "unavailable" to respond to Mr Adam's criticisms. Earlier this week the firm defended the latest price hike when the spokeswoman said: "McGill's passengers still have access to some of the cheapest bus fares in Scotland."