Home Secretary Charles Clarke has defended plans for a new points-based immigration system for workers who want to come to the UK from outside the EU.
The system is likely to be similar to those used in Australia and the US
The scheme is designed to make it easier for highly skilled, younger workers to enter the country.
But it will be harder for low-skilled, non-EU workers to head to Britain.
Mr Clarke says the system will simplify immigration. But Tory Damian Green says the scheme is an "implicit admission that the current system has failed".
"The government has no control over our borders and no proper information about the most basic facts and figures," the shadow immigration minister said.
While he welcomed the principle of a points-based system, he argued that there were serious questions to be answered about the plan.
However, Mr Clarke, answering an emergency Commons question on the issue, told MPs that Britain needed to protect itself from people trying to abuse the immigration system.
FIVE IMMIGRATION TIERS
Highly skilled migrants, including doctors, engineers, finance experts
Skilled with job offers - Best example would be teachers or nurses, or other jobs matching NVQ level 3/A level if they have a job offer in a "shortage area"
Students and special sectors such as sports people and employees of international companies based in the UK
Visiting workers, such as musicians, working holiday visa holders
"The UK needs a world class migration system to attract the brightest and best from across the world, while being robust against attempted abuse," he said.
"This new system will give employers and education institutions a stronger role in the managed migration system and introduce a more transparent and objective method of points-based structured decision-making."
Like similar regimes in Australia and Canada, points would be earned for factors such as qualifications, work experience and language skills.
A certain number of points would be needed to be considered for a work visa, awarded for aptitude, age, experience, and the level of need in each sector.
Highly skilled workers such as doctors, engineers and IT experts would get the most points under the system, due in place from mid-2007 at the earliest.
They will be the only group able to come to Britain without a job offer.
But skilled workers, like nurses, teachers and plumbers, would be able to come to the UK if they can plug shortages in the workforce.
A person applying as a low-skilled worker would be granted entry to fill specific job vacancies for fixed periods, with guarantees that they will leave at the end of their stay.
Other applicants would include students and special sectors such as sports people and employees of international companies based in the UK, plus visiting workers - such as musicians or those on working holiday visas.
Low-skilled workers, students and visitors would only be allowed entry if their home country has a formal agreement with Britain.
However, ex-Europe Minister Keith Vaz said he had reservations about the scheme because it would not address skill shortages in certain areas, like the numbers of chefs needed in south Asian restaurants.
He said that while there were 10,000 south Asian restaurants in the UK, contributing £3.2bn to the British economy, there were 20,000 vacancies.
Liberal Democrat home affairs spokesman Nick Clegg said immigration had become a "political football" and that the measures would need "proper scrutiny".
The Home Office says the scheme will not prevent overseas companies sending some staff to the UK on a temporary basis.
Mr Clarke said the new regime would replace 80 different routes into the country.
The government wants an advisory board to decide which skills are most needed.
Danny Sriskandarajah, from the Institute for Public Policy Research, said the scheme would only work if it was flexible enough to find the right workers for the right jobs.
Habib Rahman, chief executive of the Joint Council for the Welfare of Immigrants, said it could lead to unskilled migrants being exploited.
Sir Andrew Green, chairman of Migrationwatch UK, said the scheme would not quell public concern about immigration as it imposed no annual limit on the number of people able to settle in the UK.