Russian police said they found remains of the animal in Rashkin's car alongside two hunting rifles nearby.
A Russian MP has been accused of illegal hunting after the remains of an elk were found in his car.
Valery Rashkin -- a politician for the opposition Communist party -- told Russian media that he was stopped by police while driving in Russia's Saratov region.
Rashkin has stated that he and his companion did not shoot the animal and had planned to report the matter to the authorities.
"I believe this is a provocation," he told the independent broadcaster RTVI on Friday.
Russian police said they were alerted to gunfire in the Lysogorsk district, 900 kilometres east of Moscow, and found a car at the scene of the incident.
"During the inspection of the car, the police found fragments of an elk carcass, an ax, and two knives with traces of blood," they said in a statement.
The two men inside the car said they had only found the animal's shot carcass and had "decided to butcher it," police added.
The driver of the vehicle also refused to undergo a test for alcohol at the scene. Authorities later discovered two weapons cases, hidden in a bush near the remains of the elk.
"In one of them there was a hunting rifle with a night vision sight, and in the second there was a tripod and cartridges," the police said.
"In addition, the cases contain a weapon permit and a hunting ticket issued in the name of V.F. Rashkin."
"A criminal case was initiated on the fact of illegal hunting," the regional interior ministry said in a statement.
Russia's Investigative Committee said they had taken over the case following "great public outcry".
"The involvement of the deputy of the State Duma of the Russian Federation, Valery Rashkin, in the incident is being verified," they added in a statement.
As a Russian MP, Raskhin holds immunity from prosecution but lawmakers can be stripped of that privilege by a vote in parliament.
He could also be dismissed by the Duma if found guilty of hunting without a license, which carries a maximum prison sentence of two years.
Rashkin recently took part in several demonstrations, claiming that the Russian parliamentary elections were marred by electoral voting fraud.