Prime Minister Boris Johnson on Sunday refused to return Britain to its "broken" pre-Brexit economy, even as the country confronts a supply chain crisis made worse by its EU divorce.

In a bullish conference message to the Tory faithful gathered in Manchester, northwest England, Johnson vowed to forge ahead with his post-Covid recovery plan to "level up" growth, and tackle priorities from infrastructure to climate change.

The government has sought to blame the global health crisis for an exodus of foreign lorry drivers since Brexit took full effect and free movement of people ended in January.

Deliveries to supermarkets have been hit, while a lack of tanker drivers has triggered panic-buying at petrol stations, forcing Johnson to call in the army to deliver stocks.

The government now faces warnings from farmers that tens of thousands of pigs could be incinerated in the coming days without an urgent influx of foreign abattoir workers and butchers.

Marshalled by a large police deployment in Manchester, more than 2,000 protesters rallied against the Conservatives on the opening day of their conference Sunday.

"We're here today because this government is totally incompetent," retired teacher Lorraine Thompson told AFP.

"Children are hungry. How can that be in this century? We're here because we have to do something to register our disgust," she said.

One anti-Brexit protest banner paraphrased a famous speech by Winston Churchill, Britain's World War II leader -- and Johnson's political hero.

"Never has so much been destroyed for so many by so few #Brexit," it read.

But interviewed by the BBC at the conference, Johnson said Britons had voted for change in the 2016 Brexit referendum, and again in the 2019 election when the Conservatives were returned to power.

"They voted for the end of a broken model of the UK economy that relied on low wages and low skill and chronic low productivity," he said.

"What we can't do in all these sectors is simply go back to the tired, failed, old model and reach for the lever marked uncontrolled immigration, with people at low wages.

"So yes, there will be a period of adjustment."

Johnson also rebuffed Conservative critics who are angry at his government's increased tax burden and state intervention.

"If I can possibly avoid it, I do not want to raise taxes again, of course not, nor does (finance minister) Rishi Sunak," he said, ahead of Sunak's keynote address to the conference on Monday.

Johnson can point to a successful Covid vaccination roll-out, which has so far seen more than 82 percent of all over-16s double-jabbed.

But anger persists in some quarters at his handling of the pandemic and a death toll of more than 136,000, as well as claims of cronyism benefiting Conservative donors for Covid contracts.

On Brexit, he has angered Brussels by threatening to shelve problematic new trading arrangements for Northern Ireland, and tensions are high with France over fishing rights.

Last week, opposition Labour leader Keir Starmer attacked Johnson as a Brexit-obsessed showman without a plan, even if his popularity remains relatively high with the public.

"We have a fuel crisis, a pay crisis, a goods crisis, and a cost of living crisis, all at the same time," Starmer told his own party conference.

Johnson meanwhile faces an outcry over the murder of Sarah Everard by London Metropolitan Police officer Wayne Couzens.

The 33-year-old marketing executive's abduction in south London in March triggered nationwide anguish and debate about the safety of women and girls.

Couzens, 48, was on Thursday jailed for the rest of his life after falsely arresting Everard on the pretence she had broken coronavirus restrictions, before raping and murdering her.

Over the weekend, the Met confirmed that Couzens had been approved for armed patrols of parliament on five occasions last year.

The London force -- Britain's biggest -- has been widely panned for advising women to flag down a passing bus if they are stopped by an officer they do not trust.

However, Johnson backed that advice in the BBC interview.

"My view is that the police do -- overwhelmingly -- a wonderful job," he said, calling on "women of all ages to trust the police".

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