The South Merthyr and Rhymney branch posted jokes about the Gurnos estate, Merthyr Tydfil, claiming it would trade on its violent reputation to bid for the Olympic Games.
"
To have a local political party who in a few months will be asking for the votes of the people of the Gurnos sneering at them in this way is really quite unbelievable
"
Huw Lewis, Labour Assembly Member
The offending pages - which also included a picture of the Queen Mother as Yoda from Star Wars - have now been removed.
Plaid Cymru - which has been targetting the south Wales valleys as one of its key areas - admitted the website was unacceptable and in very poor taste.
Ann Mahoney, a member of the Gurnos Labour Party and a resident of the estate, said people were furious about the comments.
"I don't class it as a joke - someone is very, very sick.
"It's just making us out to be complete animals."
Bad reputation
She said the jokes were damaging at a time when people had been working hard to rid the area of deprivation and its negative image.
"The crime rate has dropped - we're coming up in the world," she said.
"I hope it doesn't affect any of the projects that we have applied for."
Huw Lewis, the local Labour member of the Welsh Assembly, described the website was "bizarre", saying the area was normally denigrated by outsiders.
"To have a local political party who in a few months will be asking for the votes of the people of the Gurnos sneering at them in this way is really quite unbelievable," he said.
"I don't think you can make a light hearted joke about domestic violence, for example, and identify a community with domestic violence which is what Plaid Cymru have done."
The website also includes a section called Huwwatch, which is critical of Mr Lewis's work in the constituency.
A Plaid Cymru spokesman described the webpages as "juvenile".
But he added that it was not the official Plaid Cymru website and did not represent party views.
He said it was not yet known who had written the controversial comments, although inquiries would be made.
But Michael Martin said that, although parliamentary rules had not been breached, he warned that Commons facilities should not be used in connection with fundraising.
He said individual MPs were responsible for the issue of their allocations of tickets to the public gallery.
Plaid Cymru offers members of its fundraising President's Club tickets to the Commons. Members pay £15 a month.
The Speaker said he had examined the club membership document and could see no breach of parliamentary rules.