The Government's target to cut net migration to the UK to the tens of thousands by 2015 is "neither a useful tool nor a measure of policy effectiveness", a group of academics has warned.
A discussion paper, published online by Professor John Salt and Dr Janet Dobson from the Migration Research Unit at University College London looked at progress towards the target since the coalition Government was formed in 2010.
In most recent figures, the Office for National Statistics (ONS) revealed a net flow of 176,000 migrants came to the UK in the year to December 2012, up from 153,000 in the year to September 2012, ending five consecutive quarters of decline.
In the paper, the authors said: " We have serious doubts that the net migration target is either a useful tool or a measure of policy effectiveness and we believe that recent experience provides a number of lessons for future migration policy, both in the UK and internationally."
Net migration to the UK is calculated as the difference between the number of people entering the country and the number leaving.
The target applies to all immigrants and emigrants, including British citizens and those from other countries in the European Economic Area (EEA).
The Government has focused its policies almost entirely on non-EEA citizens, the paper says, making big cuts in the highly-skilled immigrants and foreign students.
The paper added: "It is not clear what happens next - where further cuts would come from, what policies would be needed to maintain a net inflow below 100,000, or what happens if an improving economy requires more skilled labour."
The paper argues that " damage" has already been done by actions to cut work-related, student and family migration including to the UK's reputation as a good place to work and study.
It adds: "Too much of the debate about international migration in the UK is about 'immigrants' as an undifferentiated group, without getting to grips with who 'they' are, why they come, the jobs they do, the contribution they make and the length of time they stay.
"And there is almost no reference to the fact that international migration is a two-way street, involving British as well as non-British citizens, which is what net migration is all about.
"The flow of people out of the country is vital to achieving the target and is something over which the Government has much less influence."
A Home Office spokeswoman said: "We are building an immigration system that works in the national interest, with net migration down by a third since its peak in 2010.
"We have tightened immigration routes where abuse was rife while still encouraging the brightest and best to come here to study and work, but more needs to be done.
"This is why the Immigration Bill will prevent migrants from using public services which they are not entitled to and reduce the factors which draw people to the UK."