GMB – which represents 600,000 workers, including local government and health service employees – estimates that there will be 3,000 fewer people working at the agency in three years' time than 18 months ago, leading to a reduction in services.
Its general secretary, Paul Kenny, said: "According to the Government, not filling jobs when people leave due to early retirement and voluntary redundancy – or not filling vacant posts – does not seem to count as a job loss. GMB disagrees.
"These are job losses pure and simple, as they are posts that are not available to young workers or others seeking work."
However, the Environment Agency has denied GMB’s claims, dismissing its claims as being based on "simplistic maths".
A spokesperson from the agency said: "We do not recognise the figure that has been quoted.
"We do have to work with a reduced budget over the next few years, but we haven't finished the detailed business planning as a result of our settlement and have no plans of redundancies on that scale."
In October last year, chief secretary to the Treasury, Danny Alexander, accidentally disclosed that the Government expected there to be almost 500,000 public sector redundancies by 2015 as a result of cuts.
The Ministry of Defence is expected to shed 20,000 workers. Manchester City Council announced last week that 2,000 jobs are to go over the next year.
The Environment Agency is a non-department public body that reports to the Secretary of State for Environment, Food and Rural Affairs. It aims to protect and improve the environment and promote sustainable development.
