I think you will find that these proposals apply to 'suspected' terrorists. That is to say people who are innocent, who have not appeared before a court of competent jurisdiction or faced any form of due process.
The terrorism Act defines terrorism very very widely and it could apply to anyone taking part in or organising wide scale protest to pursuade the Government to alter it's policies and think again!
The Proceeds of Crime Act already gives the Government draconian powers to remove the assets of convicted criminals through the Assets Recovery Agency
It may be regarded as a 'smash and grab' raid on the funds of organisations that the Blair or any future Government do not like very much and who might have the capacity to influence public opinion.
Note how Blair et al continue to use the word 'suspected' before 'terrorist' or 'criminal' and ignore the term 'convicted' just as they ignore the rule of law both at home and abroad. Indeed, Blair is on record as saying that he wants to "bully hound and harry suspected criminals out of the country"
He also wants to remove the guarantee against torture from suspected terrorists!
Brown is set to replace Blar and this proposal of his shows that he is just as dangerous and authoritarian.