Capping the number of people allowed to come to live and work in the UK would be “meaningless”, Labour’s leader in Wales has said.
Carwyn Jones was referring to proposals in the Conservative manifesto that net migration should be reduced to less than 100,000 a year.
He warned a cap could result in fewer doctors and nurses being recruited in Wales.
But UKIP said caps were designed to prevent oversupply not undersupply.
Speaking on BBC Wales’s Sunday Supplement programme, Mr Jones said: “Now, if we introduce a cap and that cap means we can’t recruit the doctors we need in Wales, then surely that doesn’t make any sense at all.”
In the past Mr Jones has criticised Labour’s UK leader, Jeremy Corbyn, for not taking a tough enough stance on immigration.
Mr Jones said he favours a system which would allow migrants to come to the UK if they have a job, or to give them three months to look for work.
But he said he did not see how having a cap on the numbers could work.
“What kind of cap are we looking at?” he asked.
“Are we looking at a cap where there’s a certain number of people for every sector? My suspicion then would be that what a Tory government would do was to look after the city of London and forget about everybody else.”
The Liberal Democrats said the Conservatives’ plan to bring immigration down to the tens of thousands was “a perfect example of chasing headlines”.
“In Wales, we have benefited enormously from the free movement of people across the EU, and Theresa May’s plans to end freedom of movement will be bad news for our NHS, our businesses, and tourism in Wales,” a spokesman added.
“We must have a fair and sensible approach to immigration, but scapegoating immigrants and fuelling division in our communities will do nothing to address people’s concerns.”
But a UKIP spokesman accused Mr Jones of “constructing a straw position to attack”.
“Sector caps are not arbitrary numbers; they are designed to prevent oversupply based on estimates for a given period, not create an undersupply,” they said.
“Further, these limits can be used to stimulate domestic skill creation and help lower the skills shortfall going forward.”
Other parties have been asked to comment.
Moving to the UK
Net migration is the difference between people coming to the UK for more than a year, and the number of people leaving the UK for a year or more.
It was estimated to be 248,000 in 2016 – a fall of 84,000 from 2015.
The Office for National Statistics estimated immigration at 588,000, with emigration of 339,000.
The difference between the two gives the total for net migration.
In 2016, the total number of people moving to the UK was made up of 264,000 non-EU citizens, 250,000 EU citizens and 74,000 British citizens.