The Snowden revelations made it clear how far GCHQ and other agencies had gone in hoovering up information about all of us, collecting ever-increasing amounts of hay in the search for a handful of needles. What we need is better magnets, not more and more hay.

Many of us hoped that the revelations would lead to efforts to improve both privacy and security. That’s why I and others pushed so hard for a full review of the Regulation of Investigatory Powers Act (Ripa) and all other legislation governing surveillance, and why we demanded more transparency reporting and a new privacy and civil liberties oversight board. GCHQ and the people who work there do an important job, but they let themselves down when they over-reach.

The first article written by the new director of GCHQ, Robert Hannigan, for the FT, is deeply worrying. One might expect Hannigan to begin his new post on a conciliatory note – recognising the need for reform and reaching out to the public. But his article does precisely the opposite. In an extremely controversial piece, he instead blames digital companies such as Twitter, Google and Facebook for the ills of the world. He has chosen to attack people who are rightly concerned about people’s civil liberties in this digital age.

No one denies that the work GCHQ does is extremely important. Our intelligence services clearly play a fundamental and crucial role in keeping us safe. But Hannigan’s argument contains a number of serious flaws.

To begin with, he blames technology for the fact that groups such as Islamic State (Isis) now use social media and the web to coordinate their terrorist activity. But to blame technology is short-sighted. The nature of technology is that it can be used for productive as well as destructive purposes.

Take the invention of the radio or the telephone. These transformed the nature of communication, allowing people to speak with one another across long distances far more quickly than could have ever been imagined. However, they also meant that those wishing to do us harm, whether petty criminals or terrorists, could communicate with each other much more quickly too. But you wouldn’t blame radio or phone manufacturers for allowing criminals to speak to each other any more than you would old Royal Mail responsible for a letter being posted from one criminal to another.

Hannigan’s second mistake is in assuming that “security” and “liberty” are fundamentally opposed. They aren’t – we can have more of one while also having more of the other. Snowden’s revelations showed that intelligence services had created back doors into web providers, and in so doing had made it easier for cybercriminals to hack into these companies’ services. They managed to weaken our security as well as invade our privacy – the exact opposite of what we want to see.

Third, Hannigan’s article is a simple assault on a handful of tech companies. His assertion that US tech giants are “the command-and-control networks of choice for terrorists and criminals” is clearly an indication that, if anything, he views these companies as enemies to fight, not organisations to work alongside.

Given that the UK relies on cooperation from these companies – which can and do help out in many instances, such as when there is an immediate threat to life – this approach is deeply counterproductive. Theresa May’s proposed communications data bill has already made cooperation less likely, infuriating UK companies that would be required to monitor what we all do on Facebook and Google, for example. GCHQ should be working with these companies, not alienating them.

Finally, Hannigan betrays a lack of consideration for British and global business. One effect of the Snowden revelations is that they threatened to derail consumer confidence in the digital economy. More than 10% of the UK’s economy is digital, and nearly all transactions rely on secure online computing. This warrants tight security. Imagine the consequences the day after it is revealed that a back door has allowed all bank transactions to be hacked.

One good point in Hannigan’s article is that he recognises the need for a public debate about privacy and security. A great legacy of the Liberal Democrats in government is that we have secured a full review of our surveillance framework, to report a year after the general election. Parliament will then have the opportunity to conduct a full public review into what our laws should look like. The aim should be to come up with a framework that upholds both privacy and security, and we must all make sure that happens.

Perhaps Hannigan should pay heed to one of his predecessors, Sir David Omand, who has written: “Democratic legitimacy demands that where new methods of intelligence-gathering and use are to be introduced, they should be on a firm legal basis and rest on parliamentary and public understanding of what is involved.” He is, of course, absolutely right. Hannigan should listen to that sage advice, rather than tilting at windmills.