You raised a lot of points. To a certain extent the answers depend on who the lender was and you may feel it would be worth saying who they were here to get a clearer picture.(posted 9279 days ago)You must, absolutely must, require the agency to account for the shortfall. You want to know *exactly* what they did.
As for whether or not it affects the purchase of your new home, that depends on the lender you've gone to. High Street lenders are wary of this sort of thing; specialist lenders much less so but it depends on factors such as how big your deposit is.
AS for the blacklist: in as much as we can tell at the moment, you need to write to the credit reference agencies. All this is detailed in the Blacklisted section of the site.
You could theoretically lose the new house if it goes to court and you lose (which depends in turn on how valid the lender's claim actually is) and if you have plenty of income. You may however have a valid reason to resist the lender's demands. And in reality people don't usually lose a second house because that messes up the second lender and lender's don't like to do that to each other.
Hope this helps
Lee