As top sportswear brands prepare to showcase their wares at this year's FIFA World Cup in Germany, companies like Nike, Adidas, Puma and Asics have been criticised by Oxfam International for not doing enough to protect the workers who make their goods.

In a new report 'Offside! Labour Rights and Sportswear Production in Asia,' Oxfam says many people making clothes and shoes for global sports brands have been sacked or threatened with violence when they have organised unions to lobby for better pay and conditions.

The aid group says that none of the big sports brands are doing enough to solve the problem - and singles out US-based Fila as bottom of the league in failing to address serious labour abuses in its supply chain.

"Workers' right to form unions is crucial to achieving the big improvements needed on the factory floor but many brands are still not willing to play ball," says Kelly Dent, Oxfam International spokesperson and the report's co-author.

She alleges little has changed since the Play Fair Alliance - including Oxfam, the Clean Clothes Campaign and Global Unions - challenged the industry to improve labour conditions in 2004.

Oxfam's year-long survey of 12 sporting labels found that one year after closing suddenly, a Fila sports shoe supplier has still not given its 3,500 workers any back-pay or severance pay.

Another case highlighted by Oxfam's expose is the Panarub factory in Indonesia which makes the Adidas' Predator Pulse boots promoted by England's David Beckham, France's Zinedine Zidane, Spain's Raul and Brazil's Kaka. 30 union workers were sacked for taking part in a legal strike increase their pay from as little as 60 cents an hour - and Adidas has allegedly refused to help the 30 sacked workers get their jobs back.

Despite this, the report says Adidas, Nike, Puma and Asics have made some improvements - and that Reebok has done the most to uphold sportswear workers' rights in Asia.

However, Oxfam cautions that the performance of the industry as a whole remains poor.

In response to Oxfam's report, the World Federation of the Sporting Goods Industry (WFSGI) acknowledges that one of the most complex issues for its members is the right to organise and the right to bargain collectively.

"Some NGOs believe that sport brands can dictate working conditions in supplier factories," WFSGI says. But "since most of the sports brands do not own the factories they cannot control and dictate but positively influence change.

"Over the years sports brands facilitated the introduction of some major improvements in labour, health and safety standards in many factories."

It adds: "The solutions to these problems lie not with us but remain largely the domain of governments and civil society.  We are prepared to work locally and globally within our spheres of influence to make a difference."