Tories were accused of “making up” immigration numbers after ditching a controversial target to cut the total.
Home Secretary Priti Patel abandoned former PM Theresa May’s failed policy in an attempt to win over Brexit supporters.
But Patel also refused to explain how the numbers will still be reduced - and claimed immigration would “soar” under a Labour government.
Labour leader Jeremy Corbyn, campaigning in Dundee on Thursday, said: “I've no idea where they get those figures from. I suspect they just, quite simply, make them up."
The SNP said the proposals are hostile to Scotland and will damage the economy.
Patel announced a Tory government would introduce a points-based system but would not stick to the long-standing promise to get net migration below 100,000 a year.
It depends on a majority victory and agreed exit from the EU.
Corbyn wants "a fair immigration process" that respects workers and recognises their need in the UK economy after Brexit.
But he is also facing a backlash from both sides unhappy with mixed messages.
On Wednesday, influential union boss Len McCluskey insisted a Labour victory must be followed by a tough line on freedom of movement.
Corbyn later said divisions would be discussed this weekend when the manifesto is finalised, but would not give a commitment that freedom of movement would be clearly defined.
He also flatly rejected any suggestion the Scottish Parliament would be given some control over its own immigration policy.
Corbyn claimed a different policy would be like putting up borders within the UK, despite an expert report last week claiming migration problems could be addressed by a Scottish policy.
SNP immigration spokesman Stuart McDonald said: “The Tories and Labour are threatening Scotland's economy and public services with their damaging hostile migration policies, which could send Scotland's working age population into decline, cause staffing shortages in the NHS and key sectors, and leave the whole country poorer and worse off - a price Scotland must not be forced to pay.
"Westminster has proven itself utterly incapable of acting in Scotland's interests. At this crucial election, only a vote for the SNP is a vote to escape Brexit and put Scotland's future in Scotland's hands - so we can deliver a fairer, more equal and prosperous society."
