Hampshire MPs have blasted plans to axe a New Forest activities centre and four similar sites across the UK.
Girlguiding UK came under fire during a Parliamentary debate hosted by Gosport MP Caroline Dinenage, who described the proposed closures as "bizarre".
Sir Julian Lewis, who represents New Forest East, added: "I have been watching this developing disaster with increasing horror."
As reported in the Daily Echo, the Foxlease complex at Clayhill, Lyndhurst, is one of five outdoor centres that are due to be sold off at the end of the year. Girlguiding UK has defended its proposal, saying it would cost more than £20m to bring the sites up to standard.
Since the planned closures were announced in May two protest petitions have been signed by a total of more than 57,000 people.
Dame Caroline told fellow MPs: "It has been an incredibly difficult few years for children and young adults.
"The damage caused by Covid is impossible to fully ascertain, but NHS figures show the number of children seeking help for their mental health has risen by almost 50 per cent since the start of the pandemic.
"We all know that outdoor activities and spending time with friends in nature are good for people's mental wellbeing.
"We need more opportunities for young people to have fun and spend time outdoors, and to socialise and be children."
Dame Caroline complained that young people were spending more time "cooped up indoors" on their phones.
"Now is the time to provide more opportunities for them to get out and do something fun and adventurous," she said.
Sir Julian suggested that the proposed closures resulted from Girlguiding UK's "disastrous venture" into property investment.
He claimed it had spent millions on its headquarters and "millions more on a hotel venture that went bust", resulting in the organisation being owed nearly £2.8m in unpaid rent.
Dame Caroline described his comments as "incredibly worrying".
She added: "The activity centres do not just serve young girls in Girlguiding, they run courses and activities and provide opportunities for all sorts of young people, including schools and many others.
"Once the centres are sold off there is no bringing them back. They will simply be turned into another relic of a wonderful past where children could be children."
Caroline Nokes, MP for Romsey and Southampton North, also spoke out in support of Foxlease.
Girlguiding UK said: "Girlguiding’s board of trustees has a responsibility to make decisions for Girlguiding that enable it to further its charitable objectives for girls.
"Our board of trustees regularly review our strategy, risk and assets and how to use our charity resources most effectively, so we can reach more girls and continue our core mission to help all girls know they can do anything.
"The refurbishment of the London HQ in the last decade created a new investment property hotel, which has generated a significant amount of income each year, without which subscriptions for our members would have had to have been much higher.
"The sale of the activity centres is entirely unrelated to the leased property.
"Girlguiding has agreed a settlement with the administrators of the hotel in relation to some historic debts owing. Funds have been successfully recovered into the charity’s account, and no historic debts remain.
"We understand that the announcements regarding the closure of British Girlguiding Overseas and our activity centres are sad and difficult news for our members and we thank everyone involved in British Girlguiding Overseas and with the activity centres.
"The operating environment has changed substantially in recent years and both these areas of work are no longer viable owing to the financial and operational risks.
"We do not receive any core recurring revenue funding from government. We rely on member subscriptions, grants, a small amount of investment income and fundraising.
"Like many charities, Girlguiding has had to make difficult decisions in challenging times with limited resources, but it is always important to be focused on our core mission, vision and purpose.
"For over 100 years, we have focused on what drives, challenges and excites girls and we remain committed to giving all girls opportunities."