LONDON, England (CNN) -- A protester opposed to the expansion of Heathrow Airport threw green custard in the face of British Business Secretary Peter Mandelson on Friday.
Mandelson: "Thankfully, it wasn't paint and I've come through it intact."
Mandelson had just stepped out of his car for a meeting on carbon emissions when the woman threw the cup of custard at him. She shouted a few words at Mandelson, who rushed inside the building, before walking away.
London's Metropolitan Police said it did not arrest the woman because "no complaint has been made as yet."
Plane Stupid, a group that opposes airport expansion and aviation-related climate change, identified the protester as Leila Deen, 29.
"It's not right that someone like Peter Mandelson can stand up and talk about being green. The only thing green about Peter Mandelson is the slime coursing through his veins," said Deen, who said she works at a poverty charity.
Deen disguised the custard in a disposable coffee cup with a lid.
"It was a grave decision that I had to take to highlight this, but we cannot have people like Peter Mandelson standing by and being applauded for his actions on climate change when he's agreed to the third runway and bullied others into that," she added.
Mandelson indicated that Deen failed to make her point.
"She was so busy throwing what seemed like green soup or something in my face that she failed to tell me what the protest was about," he said. "Thankfully, it wasn't paint and I've come through it intact."
Mandelson said he wanted to get on with his meeting "and not bother too much with adolescent protests." Watch Mandelson get "slimed" »
It was the second high-profile action this week by Plane Stupid, which has become known for headline-grabbing stunts.
Tuesday, nine of the group's protesters broke into the grounds of Aberdeen Airport in Scotland and delayed flights for several hours in a demonstration over expansion.
The British government voted in January to approve a controversial third runway at Heathrow, saying it will increase airport capacity and is essential for British business. The government has promised noise and emission levels will actually be reduced as Britain meets European Union targets.
Heathrow currently operates at 99 percent capacity.
The runway's construction would involve razing areas around the airport, including an entire village and parts of two other towns. Opponents say emission levels will actually increase under the plans.