It’s been several weeks now since a Conservative Party Conference many would rather forget. But unfortunate gaffs and squabbles aside, there was another matter MPs would be best off pretending never happened.

In a frankly shocking announcement, Home Secretary Amber Rudd proposed throwing anyone who repeatedly views extremist material online in jail for 15 years.

Let’s get this straight – she’s talking about people who look at detestable stuff on the internet but do not carry out any terrorist acts. She is advocating criminalising thoughts, even if they are never acted upon.

To be found guilty of a crime in law, a person must have both committed a criminal act and possess the necessary state of mind. Guilt can’t be established if one exists without the other. And so, preparing for and committing acts of terrorism should of course be criminalised, but watching terrorist content without doing anything should not.

Amber Rudd shouldn’t just take our word for it. Max Hill QC warned this week “we do not, and should not criminalise thought without action or preparation for action”.

The Home Secretary appointed Mr Hill as the Independent Reviewer of Terrorism Legislation herself, so it’s not unfair to suggest she listen to him from time to time.

Blurring the boundaries between thought and action as Amber Rudd is proposing would undermine the bedrock principles of our criminal justice system. And once the need for ‘action’ has been removed from one area, a dangerous precedent has been set where any one of us might face the full force of the law for thinking or reading something the state considers dangerous, even if it does no one any harm.

It would also be absurd to suggest this new ‘thought crime’ would only sweep up would-be terrorists and murderers. What about journalists or researchers? What about anyone just curious about the world? Well, the Government says there will be a defence of ‘reasonable excuse’ for academics, the press or others “who may have a legitimate reason to view such material”.

But this defence will only be available after the police have kicked in your door, taken you away and you appear in court – a terrifying ordeal which will have a chilling effect on innocent exploration of issues, freedom of expression and our famed free press.

And history tells us that fighting poisonous ideas through censorship simply doesn’t work. The only way to effectively challenge and dismantle repugnant ideas is to do so openly. If we simply allowed the state to dictate which kind of speech and thought is okay, how many crucial protest movements would have been shut down and dissenters prosecuted in recent decades?

The Government’s difficulties with defining ‘extremism’ are also well-documented. Pretty much any religious leader, politician or enthusiastic sports fan could fall into that bracket. But last week Amber Rudd insisted that not knowing what counts as extremist material won’t stand in the way of getting this new offence on the statute book.

The Home Office has lawyers – Liberty has come up against them once or twice over the years – and they would do well to warn their boss she’s wading into very choppy waters here.

And Max Hill QC – an eminent lawyer – has consistently said there isn’t any need for more counter-terrorism legislation, making clear we have “provided for just about every descriptive action in relation to terrorism, so we should pause before rushing to add yet more offences to the already long list”.

The Home Secretary is politicising the criminal law in an attempt to look tough on terror. She’s doing it at the cost of free speech and a fair justice system. The reality is there is no evidence of a link between viewing ‘extremist’ material and intending to commit crime, no evidence censorship will defeat terrorism, and no need for more counter-terror powers.

Mr Hill will be in post for at least another two and a half years. For all our sakes, let’s hope Amber Rudd starts to take his advice before he gets tired of offering it.

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