In her 2003 book Stasiland, Anna Funder documents what life was like for millions of people in East Germany, the inaptly named German Democratic Republic, before the fall of the Berlin Wall. She describes the way the Stasi kept control by spying on people, recruiting half a million people to spy on their neighbours or members of their own families, tapping phones, generating files on their fellow citizens which, laid upright end to end, would have formed a line 180 kilometres long.
In East Germany, political prisoners were jailed. People who attempted to leave were arrested, or even shot as they crossed the border. East Germans voted by approving the only name on the ballot paper, or by putting a line through it. Those who chose not to support the approved candidate - the ballot was not secret - could lose their job or be expelled from university, and would come under close surveillance from the Stasi.
You might think that, whatever arguments and differences British politicians have with each other, we can all agree that nobody wants to change our open, democratic society into anything like East Germany. We have our arguments in public, we campaign for support, we win or we lose and we argue again.
Yet in describing Ed Miliband's superb speech  to the Labour Party conference last week, David Cameron was quoted in the Sun  as having said, “He might believe in One Nation, but I thought it sounded more like East Germany than Great Britain.”
He might think this is funny. It's unlikely he thinks it's clever. You can tell by the mess he's made of the economy - a double-dip recession and borrowing going up - that David Cameron isn't any good at economics, but surely he's better at history than this. He surely doesn't believe it. If he does, he needs to explain himself.
Here are some of the things Ed Miliband called for last week. Better vocational education and more apprenticeships. A proper split between high street and casino banking. Making it easier for businesses to plan for the long term. An end to rip-off pension charges. I don't know why those things sound like East Germany to David Cameron. They don't sound like East Germany to me. A divided Germany is not the most obvious model for a one nation politician.
The last thing we need in this country is to import the worst elements of US Tea Party politics into our own. It's dishonest, it's fatuous and it debases our politics. We don't need to start comparing our opponents to regimes which in reality epitomise worse evils than anything we see in Britain today, either on the mainstream left or the mainstream right. We don't want politics in which offensive caricatures take the place of arguments, or in which a genuine issue of conscience like abortion  becomes a party political dividing line.
I'm sending David Cameron a copy of Stasiland. I genuinely hope he reads it. And then I hope he will realise that he made a bad mistake in stooping so low as to invoke one of the most despicable regimes of the 20th century in describing a contemporary mainstream British political party. I hope the Prime Minister will reflect on what he said, and take it back.
Tristram Hunt is MP for Stoke-on-Trent Central.