Britain’s top medal prospects in athletics, including Phillips Idowu and Kelly Sotherton, face renewed pressure this weekend to sign a controversial contract to raise sponsorship for the 2012 Olympics campaign. The Aviva World Trials & UK Championships in Birmingham is expected to raise tensions as athletes refuse to sign the Team 2012 agreement that would grant certain image rights to a sponsor.

It is thought that Visa or BT are in line to buy a £5 million package of rights, including three appearances a year from each athlete in a deal mixing medal-winners with unknowns in promotional campaigns. Agents say that the scheme will limit their clients’ earning potential and questioned the timing with the World Championships in Berlin looming next month.

“Athletes should have performance on their minds without pressure being exerted on them to sign such a significant document,” Jonathan Marks, who represents Idowu and Sotherton, said. “Athletes believe that between now and 2012 this will compromise their commercial value.”

UK Sport, via governing bodies, has issued veiled threats to withdraw funding to anyone who does not sign the contract. In a leaked letter, Niels de Vos, the UK Athletics (UKA) chief executive, said it was essential that the Games’ biggest sport supported the initiative. UKA is under pressure to bring its athletes into line or risk its future funding.

“I fully appreciate that your primary focus right now is preparation for Berlin but unfortunately our funding agreement with UK Sport means we cannot delay action on Team 2012 until post-Berlin,” De Vos said. UKA said athletes’ performance this weekend would not be compromised.

The 200 Lottery-funded athletes resisting Team 2012 include the biggest stars from last year’s Beijing Olympics, such as Victoria Pendleton and Rebecca Adlington. They have yet to receive their annual Lottery grants, worth up to £70,000 a head, which were due in April.

The Team 2012 scheme was devised to fill a £50 million financial hole after the Beijing Games. UK Sport has persuaded 1,000 athletes that they can opt out if subsequently offered a conflicting sponsorship deal.