Sefton Central Labour MP Bill Esterson is calling on the government to take action to protect the greenbelt by ensuring that brownfield sites are the first to be built on.
Bill said suitable brownfield sites must be the first locations in Sefton for any planned new housing - but this can only happen if the money is available to deal with contaminated land.
Developers however are drawing up plans to build on greenbelt land in the borough. David Wilson Homes is planning to build 270 homes on greenbelt land in Formby, while another developer has announced plans to build more than 500 homes on greenbelt land in Lydiate.
Bill Esterson quizzed Secretary of State for Communities and Local Government, Eric Pickles MP about the issue.
Speaking in Parliament Bill said: "Developers in my constituency tell me that they can make far more money building on the green belt than on brownfield sites. Is not the reality that decontamination of brownfield sites in boroughs such as Sefton is needed to protect the green belt and boost the economy?"
In response, Mr Pickles said: "The truth is that we are making money available to ensure that contaminated brownfield sites can be dealt with. He is making an enormous mistake in suggesting that all brownfield sites are undevelopable; that is entirely wrong. Some brownfield sites are green and some greenfield sites are brown."
The Secretary of State then went on to say: "The green belt remains very safe and sound in coalition care. The position is clearly laid out in the national planning policy framework, and the bill does not affect the green belt one iota."
But Bill Esterson said the Tories and Lib Dems in Government were playing politics with the country's greenbelt.
Bill said: "Eric Pickles, the Tories and Lib Dems in Government are saying one thing, but encouraging developers in to do another.
"They introduced the National Planning Policy Framework which gives the greenlight to building on the greenbelt.
"Instead of Mr Pickles usual doublespeak, I want to hear him and his fellow ministers state categorically that the greenbelt should not be built on. If he is serious about protecting the green belt, he needs to make sure that the money is available to decontaminate brownfield sites so that they can be developed instead. Developers will build on brownfield land but only if it is cost effective.
"He refuses to do that, but instead opens the floodgate for developers to build on our greenbelt in Formby and in Lydiate directly against the community's wishes.
"This isn't localism. It is the Tories and Lib Dems riding roughshod over the community and looking after the interests of big business developers."