Green MEP Keith Taylor called the proposed energy station at the Western Docks, 250m from the nearest homes in Millbrook, “totally inappropriate” for the area.
Mr Taylor said Greens had “deep concerns” about Helius and other energy companies portraying biomass as a “green” alternative to fossil fuels.
He accused the developer Helius Energy of seeking to mislead people into thinking there is no alternative to a power station.
Local residents are campaigning against the power plant while the councillors from all parties have voted to oppose it.
Mr Taylor has rejected all three of the revised designs Helius has put forward in its latest consultation which ends on Friday.
He said: “In my book this is nothing like a proper consultation. A proper consultation would ask for people’s genuine views about whether a power station is needed in this location in the first place”.
The MEP added: “Helius must take into account community concerns before it imposes a mega power station just 250 metres from people’s front doors.
“It must consider the important environmental and social impacts of the station. I believe this proposal is a totally inappropriate development for this area. If there is an energy shortfall in Southampton we would be much better to create renewable energy from wind, solar and tidal power.
“That way we create jobs, save on energy bills and reduce carbon emissions – what’s not to like?”
Helius planning director Paul Brighton insists the proposed 100-megawatt power plant, which could generate enough electricity to power 200,000 homes, is needed to help cut the country’s carbon emissions.
It will burn up to 800,000 tonnes of wood fuel each year, mostly shipped in through the docks from abroad.
Mr Taylor said growing, transporting and burning biomass was having a “devastating effect” on many people and the environment, both in the UK and around the world.
He said latest evidence showed demand was set to quickly outstrip worldwide supply and the Greens in the European Parliament have been working to try to change the law.
The Department of Energy and Climate Change (DECC) last week maintained its current support for biomass as it unveiled a new range of subsidies for renewable energy. There was a ten per cent cut in support for onshore wind farms.
Helius said it intends to submit a planning application by the end of the year.