Brendan Barber, TUC general secretary has written about the Tax Gap on his Guardian blog. As he notes:

While many worry about the growth of social division, few have had any practical solutions. The TUC does. You may not be able to limit income in a free society, but you can at least make sure people pay a fair rate of tax. We therefore show how to close the tax gap and raise these sums without increasing a single tax rate. This can be done by simply reducing the loopholes that are widely used to cut the tax bills of big companies and the super-rich.

That's why I worked with the TUC on their new tax report: this is a goal worth achieving.