Sir Keir Starmer has promised the government's new immigration measures will mean net migration falls "significantly" over the next four years.
The prime minister unveiled plans to ban recruitment of care workers from overseas, tighten access to skilled worker visas and raise the costs to employers in an effort to curb near record net migration.
He did not set a precise target, but the Home Office estimated the policies could lead to a 100,000 drop in immigration per year by 2029 - based on analysis of just eight of the core policies where "a quantitative assessment" could be made.
Conservative Leader Kemi Badenoch said: "This is nowhere near the scale of the change we need to see."
Successive governments have tried unsuccessfully to reduce net migration, which is the number of people coming to the UK minus the number leaving.
Net migration climbed to a record 906,000 in June 2023, and last year it stood at 728,000.
Sir Keir argued the proposals bring the immigration system "back into control", denying it was a response to the electoral success of Reform UK.
The PM said the new plans, which tackle legal migration to the UK, would ensure a "selective" and "fair" system, where "we decide who comes to this country".
"Every area of the immigration system, including work, family and study, will be tightened up so we have more control," he said.
"Enforcement will be tougher than ever and migration numbers will fall."
The government will scrap a visa scheme, set up by Boris Johnson's government, that allows firms to hire health and social care workers from overseas.
Instead, firms will be required to hire British nationals or extend the visas of overseas workers already in the country.
Home Office figures estimate this change will cut the number of workers coming to the UK by between 7,000 and 8,000 a year.
However, care companies warned some services will struggle to survive without international recruits.
Employers will also be asked to pay more to hire foreign staff.
The Immigration Skills Charge will increase by 32%, leading smaller firms to pay up to £2,400 to sponsor workers to come to the UK, while large firms will pay up to £6,600.
Universities could also be hit by higher charges. The government plans to look into a new tax on every international student enrolled in a UK university, with the proceeds redirected into skills training.
At the same time, colleges must meet stricter thresholds, with at least 95% of international students expected to start their course and 90% expected to finish.
The qualification requirements to apply for a skilled worker visa will go back up, reversing changes made under Johnson's government.
It will mean new applicants will generally need a degree-level qualification, rather than the equivalent of A-level, which ministers say will make around 180 job roles ineligible for the visa route.
Lower qualification requirements will remain for sectors facing long-term shortages, or those considered key to the government's industrial strategy.
However it is not yet clear what that means in practice, and the government's migration advisory body has been asked to recommend roles for inclusion.
The government also said:
- English language requirements for all work visas would increase
- The amount of time migrants need to live in the UK before applying for settled status would double from five years to 10, while setting up a fast-track system for "high-skilled, high-contributing" people
- A "limited pool" of refugees and displaced people recognised by the United Nations' agency responsible will be eligible to apply for jobs through existing skilled-worker routes.
The government will also explore changing the law on how the right to a family life contained in Article 8 in the European Convention on Human Rights (ECHR) is applied in immigration cases.
The government has previously said Article 8 should be interpreted "much more narrowly", opposing its use in cases including that of a Palestinian family, who were granted the right to live in the UK on appeal after originally applying through a scheme designed for Ukrainians.
Government sources indicated a parliamentary vote on the plans was likely, to clarify Parliament's view to the courts.
