Sefton Central Labour MP Bill Esterson said the Conservative-Liberal Democrat government's budget has given the greenlight to the destruction of the greenbelt.
In the small print of the budget, the Tories and Lib Dems have relaxed planning regulations which have been in place since 1945.
The new rules mean that the greenbelt will no longer be protected which could result in new developments cropping up on greenfield sites in Melling, Maghull, Aintree, Hightown, Ince Blundell, Formby and Lydiate.
Sefton Central Labour Action Teams are opposing any plans to build on land against the communities' wishes.
The party is organising a public demonstration on Saturday, April 16 from 10.30am in Central Square when they will be collecting names on petitions opposing the destruction of the greenbelt.
Sefton Central Labour MP Bill Esterson said: "The greenbelt is a fine achievement of the 1945 Labour government and one of which I am very proud. The Conservative-Liberal Democrat government have spelled out plans which will see its destruction.
"The views of the local resident must be taken into account before any plans are given approval. But now we face the prospect of developers riding roughshod over the views of local residents.
"It is locals who know full well the impact of increased housing on the local infrastructure, including shortage of school places, shops, GP surgeries, roads and bus services.
"New developments should look after those people already here not just those who will be here once the development is completed. It is a sad fact that the new rules will make it easier for developers to build on our valuable greenbelt.
"The Conservative-Lib Dem budget may have given the greenlight to the destruction of the greenbelt, something Labour in Sefton Central will do our best to oppose."
Aintree resident and Molyneux Ward Labour Action Team leader Marion Atkinson, who is also Labour's candidate for the ward at May's local elections, said residents throughout Aintree and Melling are concerned by the Tory-Lib Dem shift in greenbelt policy.
Marion said: "I've been inundated with calls from people who say the Lib Dems and Tories are betraying the local communities.
"Living in Aintree I know full well just how stretched the roads are already in Aintree. The congestion here at times can mean you are regularly stuck in traffic for as much as 45 minutes. And that isn't unusual.
"If you take into account an increase in housing, then we have a real problem, but not just on the roads, also on local schools and NHS services."
Maghull Labour Action Team leader and Labour candidate for Sudell Ward in May, said people throughout Maghull were "vehemently opposed" to the destruction of the greenbelt.
Patrick said: "What the Lib Dems and Tories are doing is tantamount to public vandalism and goes against the wishes of the local community.
"It is the same old story of the Conservatives and Liberal Democrats looking after the interests of big business. This gives the greenlight to developers to step in and take advantage of premium land.
"Meanwhile it is the local community which will suffer.
"We are opposing these plans and will be taking to the streets to make sure that we do everything we can to fight this and stop the Lib Dems and Tories in their tracks."
Bill Esterson added: "I am confident that we will get considerable support in our campaign to oppose these plans. We will be collecting signatures for a petition during our public demonstration in Maghull and giving out leaflets to let people know exactly what could happen.
"I urge people from throughout Sefton to join us and add their names to the opposition."
Sefton Central Labour Party will be holding a public demonstration in Maghull Central Square on Saturday, April 16 from 10.30am.