Why are Premier League shirts so expensive?

The average price of an adult replica Premier League kit has increased by 50.7% over the past decade. For juniors, the corresponding figure is 46.8%.

Hundreds of supporters from multiple clubs have told the BBC the price of official football shirts has driven them to buy counterfeit strips instead.

Half of the clubs in the Premier League charge £85 for a full-price basic adult men's shirt. Prices at the other 10 clubs start from £60.

So why are genuine replica kits so expensive?

Based on market research by Dr Peter Rohlmann, an analyst who specialises in football merchandise, a Premier League shirt costing approximately £85 can be broken down into:

Shadow sports minister Nigel Huddleston is concerned about pressure on supporters to keep up with increasing prices.

"Shirts form a large part of a club's identity, but rising costs mean the next generation of fans risk not having this important connection, while also forcing current fans into the counterfeit market," he said.

Asked if action should be taken to reduce prices, Huddleston said: "While pricing and sales are commercial decisions for individual clubs, I would hope that clubs will consider doing what they can to make authentic shirts as accessible as possible - including for junior fans in particular."

In response to a request by the BBC, the Premier League pointed to its rules, which state clubs "are free to sell, advertise and display for sale replica strip supplied by such manufacturer at whatever price they may choose".

Manufacturers argue that a great deal of research and production goes into creating an elite football strip, and that changing market trends can leave them vulnerable.

Rob Warner - formerly a kit designer for Puma and Umbro - said: "It varies by brand, and by individual designer, in terms of how much technology goes into them.

"A lot of the profit margin is made by the retailer because they're so dependent on the success of the team. During my time at Umbro... retailers would buy a million England shirts, and if England got knocked out of the group phase, suddenly they've got a load of shirts that are worth nothing. It's a risk."

Asked why prices had risen sharply recently, Warner said: "The machinists are more skilled... the techniques that are used to create badges and logos - it's all better quality.

"Then you factor in the cost of the kit deals going up, and the brands having to try to recover some of the money they're paying to the elite clubs."

The BBC contacted all nine kit manufacturers for Premier League clubs - Adidas, Castore, Joma, Hummel, Macron, Nike, Puma, SUDU and Umbro - for comment.

With prices rising, there's evidence more and more supporters are buying counterfeit strips.

Border Force - the organisation which carries out immigration and customs control - says it is seizing more counterfeit goods than ever.

The BBC was given permission to film at East Midlands Airport as officers unpacked dozens of suspected fake football shirts from just a few of the hundreds of intercepted parcels.

The seizure of these strips is often the result of investigations by both the Intellectual Property Office (IPO) and Border Force.

"Counterfeits coming into the UK cost the economy up to £7bn, and we know that it involves potentially 80,000 job losses as well," says Andy Cooke-Welling, director of enforcement and intelligence at the IPO.

"A large part of it is from the football industry, and what we'll see with the World Cup next year are spikes in demand and therefore more profits going to criminals when counterfeits are purchased."