Willie Rennie takes up Bedroom Tax issue with Danny Alexander

"I am in constant dialogue (with the UK Government) because I've gathered evidence myself, I've seen people who are going to be affected by this. I'll be working to make sure people are not hurt."

So said Scottish Lib Dem leader Willie Rennie about the problems associated with the so-called Bedroom Tax on yesterday's Sunday Politics Scotland.  In April, Housing Benefit will be allocated on the basis of the size of properties you are judged to need by a number of pretty inflexible and unfair criteria. For example, a divorced dad who has a spare bedroom for when his kids come to stay will lose out. As will disabled people who need a spare room for carers or equipment. And then there was the case raised at PMQs last week about a mum who stands to lose out because her son is serving in Afghanistan.

I was Willie's caseworker when he was MP for Dunfermline so I know a fair bit about how he works. He's very good at understanding the practical realities of policies so I expect that he will have given ministers real evidence and also some reasonable, sensible and helpful recommendations as to how they should proceed to resolve the problems this measure creates. In the same way he's worked constructively with the SNP on minimum alcohol pricing and the budget, he'll be working with UK ministers to try to get them to change things to help vulnerable people.

It's really important that these measures get changed. Even if it were possible for some people to move into smaller properties, it's not as if councils and housing associations have them to hand out. Because of earlier cuts to Housing Benefit, a lot of the new build one bedroom flats in the private sector are out of reach to someone on a low income so there is, literally, nowhere for them to go.

Those who are going to be affected by this should know that they have Willie on their side. I would expect his views to be well received Liberal Democrats in the Government, too. Let's just hope that that's enough to make a difference before it's too late.

You can see the whole Sunday politics report and debate here.