|UK Sikhs join 'headscarf' protest|
Labour's John McDonnell, Bob Ainsworth, and Fiona MacTaggart joined protesters including Sikh World War II veterans.
One organiser said making Sikhs remove their turbans was like making people "walk around naked".
The proposed law still has to go the upper house, the Senate, for approval.
Sikhs protested when the French foreign minister visited India
Saturday's demonstration was organised jointly by Akhand Kirtani Jatha UK (AKJ) and the British Sikh Council.
Jagroop Singh of AKJ said Sikhs were not reassured by a recent statement from French foreign minister Dominique de Villepin saying a "satisfactory" solution would be found for the Sikh community.
"Sikhs find it difficult to understand how this solution will be satisfactory, given that he also stated any solution would be within the constraints of the new law," he said.
French Sikhs are angry the legislation was not put before their 6,000-strong community during the consultation process.
"The greatest irony is that a large section of the 138,000 Indian troops that fought in Belgium and France during World War II were turban-wearing Sikhs," Mr Singh said.
"These soldiers breathed their last upon French soil, defending France's right to liberty and freedom."
Sikhs from across Europe protested in Paris against the proposed law on 31 January.
A further protest was held in Delhi, India last week, during a visit from Mr de Villepin.
Mr Singh added that the French Government needed to understand the significance of the turban.
"Sikhs view the turban as much a part of their body as their limbs.
"Walking around without the turban upon one's head is the same as walking around naked; it is unthinkable and completely undignified."