The proposed immigration cap could affect fewer than one in 100 migrants entering the UK, a report has found.
The Government will need to look at other routes, including international students and those joining family members in the UK, if it is to fulfil its pledge to cut net migration from 196,000 to the tens of thousands by 2015, the report by the Commons Home Affairs Select Committee found.
Migrants may even have to be stripped of their right to settle in the UK in the long term to bring the numbers down, the MPs said.
Their report found that even if visas were refused to all economic migrants taking up job offers or seeking work from outside Europe, numbers would be cut by less than 20%.
And a 5% cap, the rate imposed under the current temporary cap, would cut numbers by less than 1%, the report found.
Other measures to cut net migration will have to be introduced alongside the cap, the committee said, adding: "It is quite clear that, to achieve the reductions it is seeking, the Government will have to make significant changes to student immigration routes."
Committee chairman Keith Vaz said: "We were particularly concerned about the potential effect on international students of a reduction in immigration, seeing as they account for around 25% of total long-term immigration each year.
"Although the Government has not yet unveiled plans for reform of student immigration, our evidence underlined the crucial importance of international students to the cultural and intellectual life, as well as the finances, of UK educational institutions.
"The Government should direct its efforts to tackling those who abuse the system - bogus colleges and visa overstayers - rather than penalising legitimate students."
He went on: "Successive governments have enacted changes to the immigration system with almost immediate effect, bypassing parliamentary conventions."
