Lindsay Lohan could be sent back to prison after failing a court-ordered drugs test.

The 24-year-old actress - who served just 13 days of a 90-day prison sentence in July after violating the conditions of her probation for a 2007 driving under influence (DUI) conviction - admitted her samples came back positive but is willing to go back behind bars if Los Angeles Superior Court Judge Elden S Fox orders her to.

Lindsay - who only served 22 days in rehab following her release from prison - tweeted: "Regrettably, I did in fact fail my most recent drug test and if I am asked, I am prepared to appear before judge Fox next week as a result.

"Substance abuse is a disease, which unfortunately doesn't go away over night. I am working hard to overcome it."

Judge Fox had previously warned the 'Mean Girls' star that if she committed another probation violation she could be put back in jail.

During a hearing last month, Fox ordered Lindsay to attend psychotherapy, drug and alcohol counselling as well as random drug and alcohol testing several times a week.

If she complied, she would be allowed to return to unsupervised probation in November.

Lindsay's lawyer insisted the star is "serious about her sobriety".

Shawn Chapman Holley said: "She looks forward to proving to the court that she's moving forward in a positive manner."