The Government is holding a crisis meeting to draw up emergency plans to provide support for children following the sudden closure of Kids Company.
It comes as the charity's flamboyant founder Camila Batmanghelidjh lashed out at ministers, civil servants and the press, claiming the organisation was the victim of a "trial by media".
Up to 36,000 vulnerable children and young people received support from Kids Company, and there are fears many could slip through the net unless immediate plans are put in place to continue services.
Richard Curtis, founder of The Root Of It, an organisation which works to raise standards in special needs services in schools, said he is attending the emergency meeting "to discuss what the next steps are".
He told the Press Association: "It's about putting in services that are going to help these children so they are not abandoned.
"If there is not something put in place very quickly it's very likely that things will start to deteriorate in those areas with those families that Kids Company has been supporting."
The meeting follows emotionally charged scenes yesterday outside the Kids Company centre in Peckham, south London, where the charity was founded 19 years ago.
Children and parents waving placards protested against the closure while staff left the centre in tears, exchanging hugs with families they had worked with.
Ms Batmanghelidjh said one child was so upset she had to talk him out of jumping off a platform in front of a train in a phone call.
The charity worked with children in London, Bristol and Liverpool, and councils, the Government and charities have all said the welfare of the children is their top priority.
Mr Curtis said an inquiry should be set up to uncover why the charity collapsed so suddenly, but in the meantime the Government and organisations need to step in "to fill that void".
He said: "I do believe there should be an inquiry into how it got into this mess, but my best hope for this afternoon would be that a plan is identified and at least the first few steps are agreed.
"The scenes we saw yesterday outside the Kids Company very much reflect how the families feel abandoned at this moment in time.
"What's important now is being able to provide and reassure them that something is being put in place so things don't spiral out of control, because a lot of the emotions come out of fear of the unknown about what is going to happen to them.
"So many of them have depended on the support of Kids Company."
Charity UK Youth said they are "working closely" with the Government to fill in the gap Kids Company has left.
Abigail Oatway, senior national programmes manager, said: "I think it is always sad when a youth organisation closes because it's a struggle to find enough youth workers to support young people as it is.
"But we have some really strong local organisations that we are pulling together, to signpost these young people to other services."
The meeting comes as Ms Batmanghelidjh claimed elements of the Government had turned on her because she is "outspoken" about child protection and knows about high-profile sex abuse.
She told the BBC: "I believe much of these difficulties are about suppressing the people who are speaking out about the child protection problem in this country."
She added: "There is much more that is being suppressed and some of it involves historic sexual abuse of children involving very senior members of the establishment.
"Some child protection police officers have come to see me to say their investigations are being squashed - ie they are unable to carry out their investigations properly and have their evidence used properly.
"There has been a culture of suppressing evidence of extensive childhood maltreatments by very powerful people. As I sit here in years to come the truth of all that will unfold."
The charity had a string of celebrity backers including rock band Coldplay and artist Damien Hirst, and was lauded by Mr Cameron as the embodiment of the Big Society.
But ministers and civil servants said its sudden collapse this week followed years of questions being raised over its financial management.
According to reports, Michael Gove said Government funding for the charity should be stopped while he was education secretary, but he was overruled by Mr Cameron.
Kids Company shut its doors yesterday after a donor pulled out of giving £3 million when they learned of allegations of abuse and sexual offences related to the charity.
Ms Batmanghelidjh said she had "honestly no idea" if the Prime Minister personally intervened to keep public money flowing to Kids Company three years ago.
And she blamed the charity's collapse on ministers, civil servants and the press.
She said: "It's trial by media. It's not everyone is out to get us, we have become a football for the media and the civil servants over the summer. It's so destructive to these children."
The Charity Commission, which regulates charities in England and Wales, said it "acted quickly" when recent claims of bad financial management came to light.
And Southwark Council insisted it has all "the necessary help in place for any young people affected by the closure of Kids Company".