Britain must “tear down” trade barriers with Europe if the economy is to prosper again, Liberal Democrat leader Sir Ed Davey will warn.

In a keynote address to the party’s spring conference in York on Sunday, Sir Ed will say Boris Johnson’s “botched” Brexit deal has been a disaster for UK business.

He will argue the country needs a far more ambitious agenda than what he says is Rishi Sunak’s aim of “mere economic survival”.

His attack comes as MPs prepare to vote this week on a key plank of Mr Sunak’s revised agreement with Brussels on post-Brexit trading arrangements in Northern Ireland.

Ministers hope the Windsor Framework will pave the way for better relations with the EU after the turbulence of recent years.

Sir Ed will say, however, that a more radical approach is needed if the UK is to enjoy a “strong and sustainable” economy.

“If you want to boost our economy, you have to repair our broken relationship with Europe,” he will say, according to advance extracts of his speech.

“You don’t need me to tell you what a disaster the Conservatives’ botched deal with Europe has been for our country.

“It’s why we campaigned against it. Why, when Boris Johnson brought his terrible deal to Parliament, when even Labour supported it, Liberal Democrats stood alone and voted against it.

“And it’s why Liberal Democrats are now the only ones with a real plan to fix Britain’s trade – to tear down the Conservatives’ trade barriers, rip up their red tape, and rebuild the ties of trust and friendship with our European neighbours.”

Sir Ed will also underline his party’s reputation as “proud internationalists”, condemning the Government’s “anti-refugee bill”.

He will also attack Mr Sunak’s decision when he was chancellor to abandon the commitment – first introduced by the Conservative-Lib Dem coalition – to devote 0.7% of national income to international aid.

“Our 0.7% commitment survived three Conservative chancellors. But then along came Rishi Sunak, ripping up that proud commitment for the UK to lead the world on aid for the poorest. How cruel, counterproductive, and unpatriotic,” he will say.

“So Liberal Democrats, we will put the UK back where it belongs. Leading the fight against poverty, hunger and disease – everywhere in the world.”