Last week the National Enquirer ran a report claiming that Culkin, 31, was spending $6,000 a month on a heroin and prescription drug problem, and that he had turned his Manhattan apartment into a drug den, alleging that he would be dead in six months due to his addictions.
Despite his rep's denial, the tabloid is standing by its original assertion, yesterday urging the former child star to "get the treatment he so desperately needs."
They hit back online, writing: "Our advice to Macaulay is to seek professional help to avoid the same tragic fate as other beloved celebrities including Whitney Houston, who died earlier this year.
"Should Macaulay's representatives continue to deny (our) accurate and detailed report, we are ready to offer him the opportunity to take a blood test administered by an independent medical lab."
The paper also referred to Culkin's friend Elijah Rosello, who died of a drug overdose in March this year, at the age of 24.