"The union cabinet is considering a clutch of bills which were not taken up in parliament during the recently concluded session," CPI-M general secretary Prakash Karat said in a letter to Mukherjee.
He said the cabinet may also propose some amendments in the Andhra Pradesh Reorganisation Act, which the president has already approved to form a state called Telangana out of Andhra Pradesh.
"If this is true, it is a shocking step which is unconstitutional and makes a mockery of parliament," Karat said.
"It will also be establishing a dangerous precedent as the creation of a new state is a serious issue and cannot be a plaything for narrow political interests.
"As for the bills which are designed to combat corruption, after doing nothing for five years, the government is now seeking the ordinance route.
"The government could have easily extended the session of parliament by a few days to get them discussed and adopted," Karat said.
The CPI-M leader said that to promulgate ordinances to suit the ruling party's interests after parliament had been adjourned, and on the eve of the election announcement, would amount to "a blatantly anti-democratic and partisan exercise".
"As the president, with the experience and wisdom of having dealt with constitutional and democratic procedures over long years in public life, I am sure you will not countenance any short-sighted and partisan measure which bypasses constitutional and democratic procedures," Karat said.
The Lok Sabha was adjourned sine die last month. It was the last session of the 15th Lok Sabha.