Shelter Scotland has started legal action against Glasgow City Council over what it claims are "failings" in its homelessness services
It follows concerns over "gatekeeping", where a homeless person is denied access to services.
The charity claims people have been illegally denied a place in temporary accommodation.
But the council said its services face "significant, perhaps unique" pressures compared to other parts of Scotland.
Shelter Scotland is now seeking a judicial review at the Court of Session, following the council's inability to respond to a pre-action letter, which set a deadline of 30 September.
Graeme Brown, director of Shelter Scotland, said: "We are not taking this action lightly. We exist to fight for people's rights to a decent home and to stop homelessness happening.
"By taking legal action we are trying to stop Glasgow City Council denying hundreds, perhaps even thousands, of people their right to a roof over their head.
"Rights are not a privilege - they are a legal entitlement enforceable by law and the council should not be allowed to disregard the law with impunity."
He also said failure to act now would allow public bodies to "pick and choose" which laws they wish to follow.
Mr Brown added: "The facts are clear; Glasgow City Council is breaking the law; homeless people are being forced onto the streets; officials are unable or unwilling to tackle the problem; and the numbers are getting worse, not better.
"So, we are taking them to court to put a stop to this unlawful practice once and for all."
Shelter Scotland has raised more than £15,000 to fund the action, through a crowdfunding campaign.
The charity hopes the action will force the council to revise its homelessness plans, including a pledge to provide temporary accommodation for every person who needs it.
A council spokesman said: "Glasgow faces significant - and in a Scottish context, perhaps unique - pressures on our homelessness accommodation, and we continue to work with the Scottish Housing Regulator and partners in the housing and third sectors to help those facing homelessness and the threat of homelessness.
"We share a common aim with Shelter and, rather than focusing on court action, we would hope it could work together with the council and its partners to ensure that these challenges are met."