'Real cost of war'
Anjem Choudary, head of Islam4UK, told Al Jazeera the move would be about "drawing attention to the reality of what's happening in Afghanistan".
"Our procession is not against the people in Wootton Bassett, we're not demonstrating against them ... obviously when people return who have died it's a very sombre occassion.
"But at the same time it's very important we explain to the general public that what the British government are doing in Afghanistan is not protecting freedom and democracy."
A total of 108 British soldiers died in Afghanistan in 2009 compared to 2,038 civilians in the first 10 months of the year, according to the United Nations mission in Afghanistan.
Choudary has written an open letter to families of the dead soldiers, saying the proposed march was not "merely an act of incitement or provocation".
"The procession in Wootton Basset [sic] is therefore an attempt to engage the British public's minds on the real reasons why their soldiers are returning home in body bags and the real cost of the war," the letter says.
No date has been set for the march, which has caused uproar in the country.
A Facebook page set up to condemn the planned procession has attracted more than 230,000 members, and Chris Wannell, a former mayor of Wootton Bassett, said Islam4Uk should reconsider.
"I know we still have freedom of speech and freedom of movement but I think that Mr Choudary has made a bad choice," he told the BBC.
"I think if Mr Choudary has any decency about him he will not march in Wootton Bassett."
Brown's Downing Street office said it would be up to the local authorities in Wootton Bassett to decide whether such a procession would be allowed.
"The prime minister's view would be obviously that anything that is considered to be offensive to, or of concern to, families of troops wounded or killed in Afghanistan would be completely inappropriate," a spokesman said.