The new year will mark the end of an era for the Royal Mail. Its postal staff will stop using the red Pashley Mailstar, once a common sight across the UK. Since 2010 Royal Mail has removed 13,000 to 14,000 bikes from its operation, leaving between 3,000 to 4,000, and in 2014 even these will be phased out entirely.

However, where Royal Mail is retracting its cycles many around the UK are doing just the opposite.

TNT Post, Royal Mail's biggest rival, delivers 95% of its mail by bike (the other 5% vans delivering to out-of-town depots where the bike takes over). Last month it expanded into Greater Manchester from west London, doubling its fleet to 1,000 bikes. Between them, TNT posties now cycle 32,000km per week, an average of 4.4km per round.

Its director of End to End (the collecting, sorting and delivery of post), Gary Robinson, sees the bike as essential to his business. He says: "Bikes are low maintenance, economical and the environmental benefits are obvious. As the roads become more congested cycling becomes more favourable. For instance I couldn't get around London as quickly in a van as I can on a push bike. Ultimately our product lends itself well to being cycled."

He said TNT hopes to have up to 20,000 posties in the next five years.

The reason for Royal Mail's bike cuts, 'elf and safety, was met with derision at the time by posties and those who argue the risks of cycling are outweighed by its health benefits.

Royal Mail says the removal of bikes reflects the changing nature of mail: thanks in part to our growing love of online shopping; with more packages and fewer letters modern mailbags are bulkier and heavier. Royal Mail will now mostly deliver on foot using trolleys which, it says, are more efficient than bicycles.

However, cycling charity CTC's campaigns and policy director, Roger Geffen, disagrees. He says: "There are plenty of operators who recognise that bike is an extremely efficient answer, you have just got to find the right bike.

"I cannot see why they think the traditional post bike isn't appropriate for the loads they're carrying. When CTC did our Keep Posties Cycling campaign three years ago, at first [Royal Mail] just ignored us, until we arrived with a very large number of letters delivered by post bike. They had actually done research into different options: there were bikes that met their needs that couldn't be produced in large enough volumes and there were bikes that could be produced but they didn't work well."

He said Royal Mail also looked at e-bikes, though above a certain weight an e-bike falls into the motorbike category.

Outspoken Deliveries, a Cambridge-based cycle delivery company, offers a post collection service from the local Royal Mail depot to guarantee delivery before 9am. Its cargo bikes can deliver up to 140 parcels per day, up to a quarter of a tonne at once. Outspoken's Rob King believes Royal Mail's price increases have helped drive competition. "I think other companies [like TNT] are doing it just because they get more and more sensible in terms of pricing," he says.

Yellow Jersey Post, a Coventry cycle courier, has delivered mail by bike since 2009. Co-director, Richard Hicks, said: "We are now delivering about 50,000 letters a month to 150 local businesses in and around Coventry, which isn't bad for four years. Those are estate agents, doctors, voluntary organisations and law contracts. We also handle a lot of Coventry deliveries for a national mail handler.

"Our standard service is the equivalent of Royal Mail's second class service, which takes one to three days. For us it is absolutely essential to use bikes, it is the only way we can do the job. If you attempted to deliver 350 letters a day by car to 250 addresses it would wear the car out and cost a fortune in petrol."

However, he concedes his operation is inherently different. "Royal Mail have very large volumes of post with each postman going door to door. For us we have only a few houses in a road. I pass five or six postmen on my round," he says.

Despite the changing nature of post Geffen still feels there is a point to prove about what freight bikes can do. He says: "There are plenty of posties that are totally convinced they could use a light freight bike, that they could find a way of spreading out the parcels. They don't like the idea that they are going to be cooped up in a van when they could be outdoors."

"As far as we are concerned this isn't the end of the story; we understand from Royal Mail their vans have a lifespan of about five years, and if they find they are being undercut by these companies or if they find the health of their work force suffers there is time to have a rethink. What they are doing is reversible."