Margaret Aspinall, who lost her 18-year-old son James in the tragedy in Sheffield, said:
“We have waited 20 years for the truth – that is 20 years too long.
“What this is all about for us is the release of police and emergency service documents which are what will help us understand what happened that day.
“There are probably 800 boxes of documents alone which have not been seen –it sickens me that these have not yet been handed over.”
The 62-year-old, from Huyton, Knowsley, Merseyside said she had still to come to terms with what had happened to her son.
More than 40 supporters of the campaign – including some Everton fans – gathered at Temple Tube station before marching for two miles in sunshine through the capital before arriving at Downing Street.
As the supporters marched along the side of the River Thames, the numbers swelled to more than 150.
Barry Thompson, from March4Justice, which organised the rally, said he was “truly overwhelmed” by the support, adding:
“This is not just about Liverpool football club, this is not even just about football – the support we have had has been tremendous.”
Rosemary Stewart, wearing full blue and white Everton gear among the crowd of mainly Liverpool supporters, said:
“These 20 years have been completely tainted by dishonesty. We demand that the truth comes out.”
The march had been organised by the March4Justice facebook group.
If you want to show your support you can click here to sign the No. 10 e-petition.