Council tax on second home

jenza8

I hope someone can help.  When i met my husband, he was living in London and I lived in the North. He eventually moved up here and we bought a house together. His work remained in the south though and so he kept his flat for him to stay at on occasions when he needed to. 
Over the last 7 years, this has been fine but this year, Harrow Council have decided to charge the premium rate of council tax (200%) for an empty property. The definition on their website of an empty property is one which is unfurnished and has been unoccupied for 2 years. The property is neither - it is furnished and it is occupied on the nights that my husband is working in the south. 
Harrow Council are refusing to change the bill despite us giving them evidence that the property is furnished.  The lady we spoke to on the phone said that Hattow are charging premium rate for second homes. Are they allowed to do this? We cannot get through to any of the senior officers to discuss this with. Evidence has to be submitted via their website and the only responses we get say they have looked into it and the premium rate still applies but they don't explain why the price rate applies. I'd be really grateful for any advice about how to deal with this. If anyone can point me in the direction of a document that shows whether a council is able to charge 200% for 2nd homes, I'd be incredibly grateful too. Thanks