The prime minister has warned Reform UK “will tear this country apart” ahead of the Labour party conference.

Arriving in Liverpool on Saturday, Sir Keir Starmer said Reform’s plans to abolish indefinite leave to remain (ILR) for legal migrants was one of “the most shocking things” Nigel Farage’s party had said.

Sir Keir said the conference would be an opportunity to show Labour’s alternative to the “toxic divide and decline” offered by Reform.

He is under pressure after opinion polls show Labour trailing Reform UK, alongside speculation Great Manchester mayor Andy Burnham could mount a leadership challenge.

Farage told the Telegraph, Sir Keir’s language “smacks, frankly, of total desperation” after the prime minister referred to Reform as an “enemy” in an interview with the Guardian.

“To call somebody in politics an enemy is language that is bordering on the inciteful,” he added.

Arriving at the conference centre in Liverpool, Sir Keir said it would be a “big opportunity to make our case to the country, and make it absolutely clear that patriotic national renewal is the way forwards – not the toxic divide and decline that we get with Reform”.

Last week, Reform UK announced it will replace Indefinite Leave to Remain (ILR) with visas and force migrants to reapply every five years, if the party wins the next election. That includes hundreds of thousands of migrants currently in the UK.

Applicants would also have to meet certain criteria, including a higher salary threshold and standard of English. ILR is a key route to gaining British citizenship and allows people to claim benefits.

According to a YouGov poll published on Saturday, abolishing indefinite leave to remain divides the public with 58% of Britons opposed to removing it from those who already hold it.

But more than 44% say they support ending ILR as a policy, while 43% are opposed to the idea.

During a visit to the office of newspaper Liverpool Echo, Sir Keir said: “These are people who have been in our country a long time, are contributing to our society, maybe working in, I don’t know, hospitals, schools, running businesses – our neighbours, and Reform says it wants to deport them in certain circumstances.

“I think it is a real sign of just how divisive they are and that their politics and their policies will tear this country apart.”

But Reform UK claim the British people have been “betrayed by both Labour and the Conservatives”.

Speaking to teenagers at the Liverpool Echo visit, Sir Keir also insisted the government would not legalise cannabis, and defended his plans to lower the voting age to 16 in general elections.

“It already happens in Scotland, already happens in Wales, and the sky didn’t fall in,” he said.

Ahead of the Labour conference, backbench MPs and unions renewed calls to end the two-child benefit cap.

Several MPs from Liverpool were among those who wrote to Sir Keir ahead of the conference insisting the cap “is one of the most significant drivers of child poverty in Britain today”.

Two MPs – former shadow chancellor John McDonnell and Apsana Begum – have had the whip restored, after a year-long ban for voting against the government on the cap.

McDonnell told the BBC: “If this is a signal the government is going to scrap the two-child limit I’m really pleased.”

The prime minister’s plans for a new digital ID system, revealed on Friday, will also likely face scrutiny at the conference.

Senior Labour figures are meanwhile expected to set out the details of a fresh tranche of “New Towns” at the event.