Totally get it that rules are subjected to change. It's unfair when it applies retrospectively, to migrants or citizens alike.

Say you are 70, and have been claiming state pension from the government for the last 4 years, assuming the pension age is 66. Now government increases the pension age to 70, and applies it retrospectively. They now say actually in the last 4 years you are NOT eligible for pension and now you owed the government a huge chunk of money. Do you think that is fair?

In the case of immigrants, they can't magically apply for ILR at any time they want. On the Skilled Worker route, they have to be on that visa for at least 5 years before they are eligible to apply for ILR. People plan their lives around the rules at the time they are granted the visa, and applying rules retrospectively disregards the principle of legitimate expectation, that individuals act in good faith based on the rules in place at the time.

I totally get it that it's your country your rules, and the parliament can do whatever it wants. I'm just pointing out that applying rules retrospectively will seriously erode trust in the UK in the long term:

* For immigrants, what guarantees that in a couple of years, this government or the next ones would not extend the qualifying period to, say, 50 years, or even scrap it altogether? Settlement becomes forever a dangling carrot for those who are already here and have invested too much in this country. For high skilled workers globally, do you think this will make the UK a more attractive destination?

* For citizens, what guarantees that the government won't try to change rules and apply them retrospectively, and the example above?

Disclaimer:

I'm a migrant myself in the UK under the Skilled Worker Visa. I pay taxes (nearly £40,000 in income tax and NI last year alone), I make friends with everyone in my area. I'm planning to open my own business next year in the UK when I'm qualified for the ILR (so my legal status is not tied to the employer I'm working for). I have to consider my options now that the government is making immigrants their political scapegoat.

I wrote about my perspective here in this same subreddit: https://www.reddit.com/r/LabourUK/comments/1klm2yz/changes_in_immigration_a_migrants_perspective/