Kim Kardashian has served Kris Humphries' ex-girlfriend with a subpoena.

The socialite's lawyers are keen to speak with Myla Sinanaj - who began dating the basketball player in January - to find out whether Kris said anything to her in relation to his claim that the 72-day marriage was fraud.

Kim's lawyer is also said to want details of hundreds of text messages and emails between Myla and Kris.

According to gossip website TMZ, Kris initially hid the relationship because he was worried it would impact on the divorce case as he and his representatives felt him moving on just over two months after he and Kim split would make it appear he wasn't "devastated" by the reality TV star's decision to file for divorce despite his previous statements.

Myla's lawyer previously admitted his client would be prepared to help Kim in her divorce proceedings.

The lawyer, Joe Tacopina, said: "My client isn't going to rule anything out at this point including whether or not she would be willing to assist Kim Kardashian in her divorce case. I will say this, Kris Humphries has to be the only 7ft man in the universe to have two women under 6ft tall bully, defraud and attempt to extort him. It's absolutely ridiculous."

Myla recently demanded Kris apologise for trying to destroy her reputation after it emerged that Kris' lawyers had contacted the FBI, claiming Myla tried to extort him by demanding a huge sum of money or she would spill secrets about their relationship to the media.

Joe said: "I defy them to show that she has asked for one red cent. I challenge them to submit Kris Humphries to a polygraph and if he does I will have my client do the same. She never asked him for a penny."