“Careless and irresponsible” is how an outraged member of the public described Twickenham MP Vince Cable’s attitude to disposing of correspondence, after finding bags of confidential and personal letters discarded in the street.

The worried whistleblower, who brought the RTT reams of evidence of the Business Secretary’s lax disposal methods, took it upon himself to bring the issue of worrying data protection practices to the fore after seeing it happen time and again since the 2010 elections.

He said: “I thought how careless, how careless to be doing that, and irresponsible too.”

The eagle-eyed passerby said transparent bags were left out in the street and he could see people’s private letters showing through the side.

He said: “I thought ‘Am I seeing correctly or not?’ and thought I better look inside. Then I realised just how extensive it was and I just monitored it to see if it stopped.

“What with all the publicity about breach of privacy by journalists, and also that some lady journalists had been there [to Dr Cable’s constituency office] and then they complained about these journalists saying they were breaching their confidence, I just thought it’s all so hypocritical for them to condemn Murdoch.

“I just thought it was the pot calling the kettle black.”

The unnamed source, who said he had no political motivations but wished to remain anonymous, checked rules regarding data disposal via the information commissioner’s website and looked up instructions on the House of Common’s advising MPs on how to treat constituents’ correspondence.

He said: “I just thought this is extraordinary, he’s not even prepared to invest in a shredding machine for the office. How mean can you get?

“I didn’t keep records of when I took stuff [but] I thought it was of public interest.

“It wasn’t taken with the thought of selling it to thieves and robbers, I just thought it was something of public interest.

“Some of the things are very personal to do with disability and health and some mental problems, and they give the full details of names and addresses and people and in some cases phone numbers.

“It is certainly not the sort of thing people would be happy to have thrown out by the GP or area health authorities or the council or any organisation.”

Shocked by the extensive details being thrown out on the street the moral crusader decided to investigate further.

He contacted people in the area whose personal details were printed on a thrown out list of BNP members to see if the assertions were true – he said they denied the suggested political affiliation.

And he also visited Richmond Park MP Zac Goldsmith’s office to see what his disposal practices were like – he said he did not see any carelessly discarded bags like outside Cable’s office.

He said: “A lot of confidential documents relating to people’s private affairs are being thrown out on the street, put out without attention to the legal requirements of how you treat confidential documents.

“Outside the door it happens every Monday evening and you will find a sack of people’s confidential correspondence dumped outside.

“This is not right [you] are supposed to treat these things with full care.

“It isn’t good enough really, and I imagine there’ll be a lot of disappointment.”

For more on this story, see today's Richmond and Twickenham Times