SP chief Mulayam Singh Yadav on Monday demanded a probe into the alleged collection of huge sums of money by BSP cadres on party supremo and Chief Minister Mayawati's birthday.

"Last year on her birthday she claimed that Rs 12 crore was collected and this time she is claiming that it has been doubled. Huge sums of money were collected. This should be investigated," Yadav told reporters in Lucknow.

"In case a thorough probe is conducted, those who wanted to send us to jail would themselves land up there," he said, in an apparent reference to Mayawati.

A PWD engineer was killed allegedly by BSP workers when he refused to contribute to Mayawati's birthday celebrations.

Asked about demands from certain political parties on the Swiss bank accounts of politicians, he said the government should also investigate how Mayawati got crores of rupees in her account.

Yadav said his party has evidence of how heavy sums upto Rs five lakh have been collected from people living in slums by BSP workers.

"We will try to make the evidence public very soon," he said.

Reacting to a recent suicide of a government employee allegedly over extortion of money by his seniors in Mahoba district, Yadav said that it was fourth such case since Mayawati's birthday in January.

"This is a dangerous trend for democracy that government employees have to end his lives because of harassment and the chief minister is responsible for it," Yadav said.