Extra stamp duty on landlords buying investment properties unfair ?

I would agree with you, Councils all over the country are dependent on individuals investing their money in houses to provide the increased need for rental homes and so by putting additional costs on these individuals it adds to their costs and so adds to the level of rent that is required to cover this, meaning rents will increase...but it just doesn't affect landlords, it affects couples who have purchased a home together, they split up and one remains in the home often with the children while the other has to go and rent somewhere and if they purchase a home for themselves it also affects them ..so more likely they will rent increasing the need for more rentals...very short sighted HMRC gaining in the short term and the country moving to a country of rental and not ownership.

What it will do is numbers of people will increase in purchasing property abroad so money will leave the country and not remain in the UK economy

It doesn't apply to companies.

So when a rental does come up for sale, it's less likely to be purchased by that individual private LL