The drug is also being sold there, Senator Edgar Artunduaga said.

"I know names of people who distribute cocaine here in Congress," he said, revealing the results of an investigation ordered by his office.

"There are important officials who distribute, and senators and representatives who consume," he said.

Personal possession of small amounts of cocaine and other drugs is not illegal in Colombia, the world's biggest cocaine producer.

Mr Artunduaga refused to name those involved.

"But I will denounce the dealers to authorities," said Mr Artunduaga, describing some of them as "middle-ranking officials".

'Smear'

Some colleagues accused him of smearing Congress.

"Artunduaga should present evidence and say who are the lawmakers that use drugs, or resign," said Armando Benedetti, a pro-government deputy in the lower chamber.

Mr Artunduaga said the investigation also exposed big holes in security at the congressional buildings.

He told the Associated Press that none of the buildings' closed circuit cameras worked, and that some 10,000 people possessed congressional security passes, but many were fake.

"Biscuit sellers, shoe sellers, astrologers and marijuana and cocaine dealers all enter Congress," he said.

The Colombian government has launched a major campaign against the cocaine trade, and the civil war it fuels, with the help of billions of dollars of US aid.