Bristol's Lib Dem city council has formally objected to the £150 million expansion planned for Bristol International Airport.
It says night noise and traffic pollution will get worse - and climate change problems will be exacerbated - if the project goes ahead.
Although the plans will be decided by North Somerset Council, Bristol can express its concerns as a neighbouring authority.
Jon Rogers, executive member for transport and sustainability at the city council, says: "The Liberal Democrats have been expressing concerns about the expansion plans for many years. The latest application fails to address many of these concerns."
The expansion would include a larger terminal, multi-storey car parks, a new runway apron and demolition of the old terminal.
The airport says the expansion is needed to cater for the increase from six million passengers to 10 million a year by 2020.
It says the effect on air quality in Bristol will be small and measures have been put forward to reduce and mitigate environmental impacts.
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