The chief minister of India's Uttar Pradesh state has said the founder of the whistleblowing website Wikileaks "needs to be in a mental asylum".
Ms Mayawati said Julian Assange was either working with her political opponents or had "gone mad". He has demanded an apology.
The outburst follows reports, based on leaked US diplomatic cables, that she sent an empty private jet to collect a pair of sandals from Mumbai (Bombay).
She flatly denied the reports.
Ms Mayawati said the charge was "mischievous, baseless, wrong and shameless".
A BBC correspondent in Delhi says Ms Mayawati's outburst is not out of character - in the past, she has often used strong and offensive language against her critics and political opponents.
But she is also an icon to millions of low-caste Dalits (formerly untouchables) who are mostly poor and deprived. Uttar Pradesh, the state she leads, is one of the poorest in India and also its most populous.
Later, Mr Assange responded to Ms Mayawati, saying she had "betrayed rational thought" and asking her to withdraw her statement and apologise.
He added that he had been held under house arrest in the UK for 272 days but "would be happy to accept asylum, political asylum, in India - a nation I love".
"In return, I will bring Mayawati a range of the finest British footwear." {Read on}