The sense of anger is hard to adequately put into words. Yesterday, in the toxic climate that now defines British politics the prime minister took to a Downing Street podium to place the blame for this national crisis on MPs. She pitted parliament against “the people”, deploying an inflammatory rhetoric reminiscent of far-right populists whose influence is steadily growing in Britain, America and across the world. Reckless doesn’t do it justice.

Frustration in parliament was already high. For nearly three years the prime minister has refused to listen, reach out or compromise – rejecting efforts to find an accommodation not just with MPs, but with the varied currents of opinion we represent in vastly different and divided communities across the country. She has refused us vital information, asked for our trust and then broken promise after promise. It has brought Britain to the brink and the strain is showing.

On Monday we debated the government’s plan to allow chemists to limit medicine in the event of a no-deal Brexit. Constituents have contacted me to ask if their medication will be available in just over a week’s time. Their own government says it cannot make any guarantees. The stress and anxiety is grinding people down and the public exasperation is turning to fury. During the referendum there was a sense of powerlessness, anger and betrayal among leave voters. Now I feel it among leave and remain supporters alike. But still the prime minister seeks to stoke division. It is dangerous.

The political choices that have brought us here have been needlessly cavalier but yesterday, with May’s Downing Street statement, politics took a darker turn. Credible threats have been made to MPs – particularly women – to our families and to our staff. The prime minister knows this, yet chose words yesterday that were incendiary and dangerous. The week after 50 people were murdered in New Zealand because of their religion we should surely know that rhetoric has consequences.

There has been a steady poisoning of our political discourse in recent years. Technology that should have opened up democracy is used to undermine it. Twitter is used as a tool to attack, condemn, separate us into tribes who see the world in black and white, or good and evil and hoax people into believing the worst of each other. It is commonplace to hear politicians rail against the mainstream media. Institutions such as the BBC and Equality and Human Rights Commission are attacked by politicians on right and left, focusing not on the debates, decisions or content of their policies or programmes but the legitimacy of the institution itself. The language of betrayal is commonplace. Judges are condemned as “enemies of the people”. Civil servants have been attacked in the House of Commons, hung out to dry in newspapers by their own government. They have faced threats to their safety.

Populism, once unleashed, threatens the basis of liberal democracy itself. Democracy is precious and fragile. It cannot survive without a willingness to cope with the complexity of the world as it is.

Yesterday in parliament I spent several hours, with my colleague Gareth Snell, trying to reassert those principles of democracy and find a route through this nightmare, by guaranteeing a role for parliament in the next stages of Brexit negotiations; we were trying to ensure that once the withdrawal agreement is passed we end this desperate tug of war and begin the messy, hard business of compromise and the search for common ground. A few hours later, the prime minister stood up inside No 10 Downing Street and trashed our democracy. She is not fit to be prime minister, does not deserve the support of MPs, and she will not get it.

• Lisa Nandy is the Labour MP for Wigan