Theresa May is under intense pressure to save the independent inquiry into child abuse after survivors groups condemned it as a mess and demanded she rip up the process and start again.

Seven months after the announcement by May of an inquiry to examine institutional culpability for decades of abuse of children, victims met in the House of Commons to voice their demands for reform of the process.

The inquiry has been beset with problems. Two chairs, Dame Elizabeth Butler Sloss and Fiona Woolf, were forced to stand down after complaints from victims that they were too connected to the establishment, and the appointed panel faces being disbanded after some survivors raised objections to its composition. No new chair has been appointed, and some victims are now pursuing a judicial review to challenge the way the home secretary set up the process.

Phil Frampton, a survivor and spokesman for the victims and campaigners who gathered in the Commons on Wednesday said: “There were more than 300 people gathered today and what was so clear was it was a demonstration of our will. We want the inquiry to go forward. At the moment it is a complete mess. What we want is for Theresa May to rip it up and start it again to put it on a sound footing, to make it fully transparent and to make sure survivors can be proud to engage in the process.

“At the moment it doesn’t have a clear purpose, the focus must be narrowed towards getting justice. When you look at MPs’ expenses, the MPs met, people were taken to court and perpetrators were jailed. That is what we want.”

Victims who gathered at the Commons on Wednesday in a meeting arranged by John Mann, Labour MP for Bassetlaw, were sent a message of support by Samantha Morton, the actress, who recently disclosed that she was abused as a child in care.

In a message read to those gathered, she said: “We will not forget, we will not be forgotten. The abuse that we suffered is happening today right now to a child that is desperately in need of rescuing. We come together as one to stop child abuse so the perpetrators of these horrific crimes can be brought to justice.”

Victims highlighted the need for a transparent statutory inquiry, with a defined remit, a properly constituted panel who were appointed openly, and the provision of professional support for victims who give evidence.

Andy Kershaw, who was abused in an approved school in Torbay in the Seventies, highlighted how in the past inquiry after inquiry had failed to bring perpetrators to justice or stop further organised child abuse. As an example, he said 4,000 victims and 190 paedophiles were identified in the investigations into the abuse at schools in Torbay but only four perpetrators were ever brought to justice.

May is understood to have decided that the inquiry, which was set up to consider whether public bodies and other non-state institutions failed in their duty of care to protect children from abuse, must become a statutory one. As a result panel members have been told they might face being disbanded in the coming weeks.

On Wednesday the barrister Michael Mansfield QC said he was more than willing to consider a request from victims to chair the inquiry. But he said it had to be properly constituted and empowered. He warned survivors this may not happen.

“As you are acutely aware … the authorities have a habit of ignoring the wishes and needs of those most affected. This has happened yet again on a massive scale until the whole process was ground to a standstill by the second proposed chair standing down. Now of course all kinds of blandishments are being offered to the survivors. I’m sure no one will be taken in and everyone will exercise circumspection.”

The Home Office said: “The home secretary is determined that appalling cases of child sexual abuse should be exposed so that perpetrators face justice and the vulnerable are protected. She is absolutely committed to ensuring the independent panel inquiry into child sexual abuse has the confidence of survivors who must be at the heart of this process.

“She has also made it clear the inquiry should be placed on a statutory footing with the powers to compel people to give evidence. She is currently considering options for doing this.”