Bexley Council has been accused of turning the borough into a "fortress" by pulling out of a scheme offering free access to some of its attractions.
The London-wide Open House programme lets visitors enjoy some of the capital’s most famous buildings – and others members of the public don’t normally get the chance to see.
But Bexley Council is one of just three borough councils out of 32 in London not currently signed on for this September’s event, which would have cost the borough more than £4,000 to participate in.
Erith and Thamesmead MP Teresa Pearce told News Shopper: "They are not having the Danson Festival and now they are not going to offer the chance for people to see these places.
"It makes Bexley separate from London like it’s fortress Bexley.
"I know it’s a non-essential service but actually it’s a celebration of the things we have to offer.
Townley Grammar School's performing arts centre will not be open to the public.
"It’s typical Bexley in that they probably don’t want people from London coming in – it’s like Bexley is for Bexley people."
As well as offering free access to well-known attractions like Danson House and Hall Place, last year’s event let visitors look round Rose Bruford College in Sidcup and Townley Grammar School in Bexleyheath.
Bexley Historical Society secretary Penny Duggan said: "Danson House and Hall Place are open to the public anyway but the whole point of Open House is to open up places that people don’t normally visit.
"For people who can’t afford to pay to go they are never going to be able to get to see them."
Open House programme manager Matt Turtle said: "We will have to wait and see how people respond to Bexley not being in Open House this year.
"Hopefully people will talk to the council and persuade them to come back in."
Councillor Don Massey, cabinet member for community safety and leisure at the time the decision was made, said: "As I have stated on many occasions recently to balance the council's finances difficult decisions are necessary.
"We have discussed participation in Open House with Bexley Heritage Trust who are an important partner in our cultural initiatives.
"For several years they have said that Open House does not assist the overall attendance levels at Danson House and Hall Place, and it also reduces the income raised.
"Local people wait for the free open day rather than pay at other times.
"As Open House costs in excess of £4,000 each year, plus officer time, I considered that it was not appropriate for Bexley to participate this year.
"This decision was taken several months ago."