French club Lens have admitted to warning Chelsea of a potential transfer ban if they pursued the signing of Gaël Kakuta.

Lens' former general manager François Collado said he met with Blues officials in London and informed them that they risked a ban if they signed Kakuta as he had a pre-contract with Lens.

The contract stated that Kakuta would sign a professional contract with Lens when he turned 17 but the Blues went against that, according to Collado.

"The contract was rubber-stamped by the French league and French football federation," Collado claimed.

"But Chelsea took him and played in a tournament with all their reserves, even without international clearance. When I met with (Peter) Kenyon and (Frank) Arnesen at Chelsea I took the contract. I told Kenyon, 'You're risking a fine and a transfer ban'. I explained the Fifa rules to him.

"Kenyon spoke with Arnesen and he said they were sure of their intentions. We said this is what we want and they said no way.

"They proposed a ridiculous fee. I said I'll leave you and if you're sure then I'll go to Fifa and we'll see if you're not sanctioned. They said there would be no need for another meeting."

Chelsea have now been slapped with a transfer embargo that will not allow them to make any signings for the entirety of 2010.