Image caption Vince Cable said the Information Commissioner's Office had been informed

Vince Cable has apologised "unreservedly" after confidential documents were discovered in bins left outside his constituency office.

Unshredded paperwork containing letters from ministers was found dumped outside the business secretary's Richmond and Twickenham office.

The transparent recycling bags also contained personal details of the Liberal Democrat's constituents.

Mr Cable said the blunder was an "unacceptable breach of privacy".

He added the Information Commissioner's Office had been notified.

The MP could face a fine of up to £500,000 if he is found to have flouted data protection laws.

'Unacceptable breach'

The paperwork was collected over a nine-month period by a local resident and was then handed to his local newspaper, the Richmond and Twickenham Times, the MP said.

The staff responsible accept that this was an entirely inappropriate way to handle such paperwork and that this was a serious error Vince Cable, MP for Twickenham

In a statement, Mr Cable said: "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."

The cabinet minister said he was alerted to the breach on Wednesday and has since instructed his office to introduce a more "secure" system for handling sensitive information.

"The staff responsible accept that this was an entirely inappropriate way to handle such paperwork and that this was a serious error," he added.

"Both I and my constituency team are dedicated to meeting the highest standards for the people of Twickenham. I am very sorry that in this instance they were not met."

'Paramount importance'

A spokeswoman for the Information Commissioner's Office confirmed it was making inquiries into the data protection breach.

"This is the second example in recent weeks of an MP or their staff allegedly mishandling constituency paperwork and again highlights the need to ensure that personal details are kept secure," she said.

It is simply unacceptable for ministers to take such a casual attitude Michael Dugher, Labour

"When constituents contact their MP they have the right to expect that the information they share will stay private - it is of paramount importance that this principle is upheld."

In October, Cabinet Office minister Oliver Letwin apologised to his West Dorset constituents after he was photographed throwing away correspondence into a park bin.

Labour said the Information Commissioner must look into Mr Cable's case "as a matter of urgency".

"Why do so many members of this Tory-led government think it is OK to throw confidential documents in bins?" said shadow Cabinet Office minister Michael Dugher.

"First Oliver Letwin and now Vince Cable - these people are completely out of touch.

"It is simply unacceptable for ministers to take such a casual attitude - it seems it is one rule for them and another for everyone else."