London Zoo is under investigation for animal welfare issues after stories of drunken parties where beer was poured over a tiger and a naked man tried to enter the penguin pool were revealed.

Westminster Council has asked for a full report after the popular Zoo Lates sessions, held every Friday night in the summer, have come under scrutiny for being overly raucous as 6,000 people descend on the world-famous zoo in Regent's Park.

The Guardian newspaper revealed earlier this month that sources at the zoo had raised concerns over the public's behaviour, with reports of alcohol-fuelled incidents including a man throwing beer over a tiger then over a staff member, a man getting naked then trying to get into the penguin pool and a drunken woman allegedly trying to enter the lion enclosure.

A zoo source told the Guardian: “During the day, welfare and conservation is of the utmost priority. In the evening, that seems to go out of the window, and the animals become a commodity. That’s not what zoos are about, but there’s a lot of money in it."

The council, who are responsible for issuing the zoo's licence, are now looking into see if the animals' welfare and public welfare are being put at risk.

Steve Harrison, the council's street management director, said: "If they are true, the stories about London Zoo’s Late sessions raise real concerns both about public safety and animal welfare. We have already asked for a full report into what happened.

"The Zoo has duties of care and clear commitments under its premises and zoo licences and we will work with managers to ensure they are upheld at any future events.”

Getwestlondon is waiting for a comment from ZSL London Zoo.