Vince Cable has apologised "unreservedly" after confidential documents were found in bins outside his constituency office.
The papers are said to include letters from other ministers and documents containing personal details of his Twickenham constituents.
The Lib Dem business secretary's error comes not long after Cabinet Office minister Oliver Letwin was caught by the Daily Mirror dumping confidential documents in a bin in St James' Park.
"I have been alerted to a breach of data security at my Twickenham constituency office," Cable said on Friday morning.
"A system is in place for shredding of confidential files and for safeguarding case work. Nonetheless, some correspondence which should have been protected was placed in bags for recycling outside the office.
"I apologise unreservedly to all my constituents for what has clearly been an unacceptable breach of their privacy."'
It has been reported that the documents were collected from the bins by one of Cable's constituents over the course of nine months, who then handed the evidence to a local paper.
The Information Commissioner's Office has said it was investigating whether Cable had breached the data protection act.
If he is found to have broken data protection laws Cable could face a £500,000 fine.
Michael Dugher MP, Labour's shadow Cabinet Office minister, said the actions of both Letwin and Cable showed the government was "out of touch".
"Why do so many members of this Tory-led Government think it's OK to throw confidential documents in bins? First Oliver Letwin and now Vince Cable - these people are completely out of touch," he said.
"This is a disgraceful way to treat constituents' private correspondence. If they can’t run their correspondence how can they run the country? It's simply unacceptable for ministers to take such a casual attitude - it seems it's one rule for them and another for everyone else. The Information Commissioner should investigate this as a matter of urgency."
Cable was recently embarrassed after he was found to have failed to pay up to £25,000 in VAT on his media work.