Under plans submitted last month 35 holiday lodges will be built on a site to the east of Ashwood Lower Lane near Kingswinford.
Developers say the scheme – which will take over a 3.3 acre site and will also include a shop, space for car parking and a toilet/shower block – will serve local tourist attractions including Ashwood Marina.
South Staffordshire MP Mr Williamson said he had written to council chiefs to express his "strong objections" and vowed to work with residents to get the plans "thrown out".
He said: “As part of my commitment to protect South Staffordshire’s greenbelt I will vehemently object any inappropriate development plans which seek to build on this protected land.
"I have written to South Staffordshire District Council to communicate my strong objections to these proposals and I will continue to work with residents and to call for them to be thrown out."
Since the plans were submitted last month they have been the subject of a string of online objections.
Anna Marie Tew, who lives nearby, said residents would have problems with increased traffic, flooding and the disruption of wildlife.
She added: "Ashwood is not regarded as a tourist attraction it is a private business and home to several residents who live here all the year round.
"I cannot see any benefits to local residents for this scheme to be granted permission and hope that the council will acknowledge our real concerns."
Julie Tranter, who says she moors her boat at Ashwood Marina, said she opposes the scheme because it will mean she will be "overlooked and no longer have any privacy".
Ian Jennings makes a similar point in his objection, while local resident Pauline Thomas says the development "will result in a total loss of privacy".
"The lanes are not suitable for the volume of traffic this development will create," she added.
A statement from RCA Regeneration Ltd accompanying the plans said the scheme will "blend effortlessly within the landscape" and "support a prosperous rural economy".
Planning officers at South Staffordshire District Council are currently considering the scheme.