Senior Tories demanded that Sir Keir Starmer rethink Labour’s approach after the Prime Minister scrapped a scheme in which asylum seekers would have been sent to Rwanda while they were processed.

The Government is under intense pressure to tackle people-smuggling gangs responsible for the crisis, and to crack down on crime committed by migrants in Britain. The Telegraph disclosed last week that one in 50 Albanians in the UK is in jail.

James Cleverly, the shadow home secretary, said: “We need to deter people from coming here illegally and to root them out of our economy when they are here.”

Robert Jenrick, the former immigration minister, who has called for the UK to quit the European Convention on Human Rights (ECHR), said: “This is the highest number crossing the Channel in a single day for years. Sir Keir needs to rip up his dangerous so-called ‘plan’ on small boats. Our country’s security is at stake.”

The up to 745,000 people estimated to have come to Britain illegally include foreign arrivals who have overstayed their visas, failed asylum seekers who have disappeared and some migrants who have crossed the Channel in small boats.

Labour has pledged to smash the people-smuggling gangs by setting up a Border Security Command to work with European and G7 partners and giving UK law enforcement and intelligence agencies new counter terror-style powers.

Sir Keir has rejected calls to quit the ECHR to help tackle the crisis, and at the weekend French and European sources told The Telegraph that Britain would only get an EU deal to send Channel migrants back to France if it remained in the European Court of Human Rights.

Illegal migrants would fill city size of Leeds

A Home Office source said: “Far from softening the response, this new Government has increased returns of those living here illegally and set up a new Border Security Command to relentlessly pursue the criminal smuggling gangs making millions out of small boat crossings, undermining our border security and putting lives at risk. We are getting a grip after the chaos of the last Government’s approach.

“The Tory leadership candidates are clinging on to the Rwanda partnership, which spent £700m to send four volunteers. Perhaps it’s time for them to learn from their mistakes, rather than simply doubling down.”

The research – published on Monday and compiled by 18 institutions including Oxford University’s Compas centre – estimated the number of illegal migrants in the UK was between 594,000 and 745,000, ahead of Germany (up to 700,000), France (300,000), Italy (458,000) and Spain (469,000).

Germany and the UK’s upper estimates accounted for a quarter of all illegal migrants in the 12 EU nations covered by the research. 

The Home Office does not publish data on the number of illegal migrants in the UK except for those crossing the Channel. Most of those are, however, not included in Oxford research because they seek asylum on arrival.

The 745,000 illegal migrants – equivalent to a city the size of Leeds – come on top of the overall backlog of 224,742 asylum seekers who are awaiting a decision on their claim, appealing a rejection, or have exhausted or not yet exercised their appeal rights.