Boat owners in Brentford have been given formal notices to move their vessels to make way for a new marina.
It plans to build a new 26-berth marina at the site, at an estimated cost of £5.45m, which it has claimed will help revitalise the area.
But those living on the boats have previously told getwestlondon they are there lawfully, having been at the site for many years, and some have criticised the proposed marina as lacking character.
They also dispute the council's claims that some boat users are reported to be illegally dumping sewage into the Thames, saying all waste is now disposed of responsibly.
Council leader Steve Curran said: "Let's be clear, these boats are moored unlawfully.
"Not only are they being unfair to owners who pay their mooring fees and those who visit the marina, but they also getting rid of waste directly into the river and trespassing in accessing their boats.
"We have sound plans to regenerate this area and want to make sure that everyone is moored there legally. We want to create a clean, safe and accessible marina that can be enjoyed by all."
Mr Curran added that the council would assist any owners to get their boats river-worthy and to find alternative accommodation if necessary.
A planning application for the new marina was submitted last September , and a decision has yet to be made.
The council began legal proceedings last October to remove the boats .
getwestlondon has contacted the boat owners for a response.
Those affected can request more information from the council by emailing firstname.lastname@example.org.