Theresa May's hostility to European leaders is not about getting the best deal for Britain, but rather about getting the best headlines in the pro-Brexit press.

The British public has been primed by decades of negativity towards Europe. A string of Tory leaders have laid the blame for every ill at Europe's door – and now even Jeremy Corbyn's doing the same.

Never mind that successive governments effectively abandoned some of Britain's poorest communities and systematically under-invested in places where industry had collapsed.

Never mind that immigration the government can control – that coming from outside the EU – has been higher than immigration from within the EU in every single year of the past four decades.

The real fault for our troubles, they say, lies at the door of the European Commission – not Number 10 Downing Street.

Conservative leaders swim against this tide at their peril. David Cameron tried to during the referendum campaign, and paid the price. Theresa May is obviously determined not to meet the same fate. Instead, she's turning the anti-European rhetoric up to eleven.

The PM has threatened to walk away without a deal, something she admits would be ruinous for our economy. She accuses EU officials of issuing threats against Britain, of wanting the Brexit talks to fail, and even of trying to meddle in our General Election.

She paints our allies as enemies, and then claims the only way to defeat them is by handing her a huge Conservative majority in Parliament – even though the EU negotiators themselves have made clear the number of Tory MPs makes no difference.

It has not taken long for May's antagonistic approach to cause problems. Before her recent dinner with EU leaders, the Brexit "divorce bill" they were proposing Britain should pay was €60bn. Afterwards, it had risen to €100bn. Just how disastrous does a dinner party have to be to cost the country €40bn?

And that's just the start. Over the coming months and years, we'll be renegotiating every aspect of our relationship with our largest trading partner. These talks will define Britain's future. But every time Theresa May gets involved, the terms of Brexit seem to get worse.

Her tough talk might win her plaudits at home, but it does nothing to advance Britain's interests on the continent. In fact, it weakens us. Her acrimonious approach will only make the EU more reluctant to give ground, and make it far more difficult to reach the good deal Britain needs.

The PM is asking us to trust her to get the best deal, even as she botches the talks before our eyes. Good negotiators can handle a bit of give-and-take; they don't conjure up conspiracy theories about their negotiating partners. Good leaders put the interests of their country first; they don't seek a short-term poll bounce for their party.

Theresa May should act like a leader. She should make every effort to build a constructive, positive approach to the negotiations and secure the best deal for Britain. But she won't; she'll stick to her hard-line hostility. Because if it all goes wrong, she can always blame the EU.

Baroness Susan Kramer is the Liberal Democrat's economic spokesperson