An attempt to make upskirting a specific criminal offence in England and Wales has been blocked by one Conservative MP.
The government had given its support to introducing the new law earlier.
But Sir Christopher Chope shouted "object" to the bill, leading to cries of "shame" from other MPs.
The campaign for the law against upskirting - where photos are secretly taken under a skirt - was started by victim Gina Martin.
Ms Martin said she was "extremely upset and disappointed" by Sir Christopher's objection, but remained "positive and hopeful".
She said she had already spoken to him and arranged a meeting to discuss the bill further with him.
Liberal Democrat MP Wera Hobhouse, who brought the private member's bill to Parliament, has criticised the "out-of-touch Tory" for "sabotaging" it.
Other MPs, including Conservative ministers and colleagues, have tweeted about their dismay at Sir Christopher's decision.
Ms Hobhouse's bill would have made upskirting a criminal offence and meant offenders could face a maximum of two years in prison.
It was expected to pass after justice minister Lucy Frazer confirmed the government would back it.
But parliamentary rules mean it only requires one MP to shout "object" to block a bill's progress.
Ms Martin said: "We knew this was a risk but I now stand with powerful, passionate women and men behind me, and I am confident that Lucy Frazer is committed to - and will - close this gap in the law."
Ms Hobhouse added: "Upskirting is a depraved violation of privacy. It is outrageous that a single member of Parliament has today been able to derail a much needed and universally supported change in the law.
"This change would have protected women and girls across England and Wales and given the police the tools to bring the perpetrators to justice. This is too important to allow people like Christopher Chope to obstruct progress on this vital issue."
Ms Martin's lawyer, Ryan Wheeler, tweeted that Sir Christopher objected to the bill because it had "not been debated".
Why did Sir Christopher object?
By Mark D'Arcy, BBC parliamentary correspondent
Sir Christopher is a leading member of a group of backbench Conservatives who make a practice of ensuring that what they see as well-meaning but flabby legislation is not lazily plopped on to the statue book by a few MPs on a poorly attended Friday sitting.
And after all this is a bill to create a new criminal offence, for which people can go to jail.
So, however worthy the cause, he insists on proper, extensive scrutiny, and he has spent most Commons Fridays for the last 20 years doing just that.
Indeed, a few minutes before he blocked the upskirting bill, he was forcing a delay to the final debate on the Mental Health Units (Use of Force) Bill, or Seni's Law, which also had strong support from the government.
The upskirting bill is not dead - there will be other opportunities to get it a formal second reading debate - but they will only succeed if Sir Christopher and his allies can be persuaded not to object again.
The only other alternative is for the government to provide debating time for it, or, far more likely, to add the proposals to a bill of their own.
Ms Hobhouse has asked for her bill to return to the House on 6 July.
After the bill was blocked, a government spokesman said they would continue to support it.
"[Upskirting] is a hideous invasion of privacy which leaves victims feeling degraded and distressed," he said.
"It cannot be tolerated, so it is absolutely right that the government supports this bill to make upskirting a specific offence.
"Whilst we are disappointed this bill did not pass second reading today, we look forward to supporting these measures through the House at the earliest possible opportunity."
Sir Christopher's colleagues have tweeted their disappointment at the bill being blocked.
Tory MP and chair of the Commons Justice Select Committee, Bob Neill, has written to the prime minister to ask for the bill to be allowed its second reading, criticising the "arcane parliamentary procedure" that stopped it.
Conservative MP and chair of the Commons Foreign Select Committee, Tom Tugendhat, said it was "shaming" for his party.
Margot James, minister for digital and creative industries, said the government was "determined" to see the bill pass.
And Scottish Conservative MP Paul Masterton said the move did "damage" to the public's view of the party.
Labour politicians, including Jess Phillips and Mayor of London Sadiq Khan, have also tweeted about their "dismay" at the incident.
What is the current law?
- There is no law specifically naming and banning upskirting in England and Wales, victims and police are currently only able to pursue offences of outraging public decency or as a crime of voyeurism
- Upskirting has been an offence in Scotland since 2010 when it was listed under the broadened definition of voyeurism
What are the limitations of the current situation in England and Wales?
- Voyeurism only applies to filming actions taking place in private
- Outraging public decency usually requires someone to have witnessed the action but upskirting is often unobserved
- Unlike other sexual offences, people don't have automatic right to anonymity
What does the new law propose?
- As well as carrying a maximum two-year sentence, it would also allow, in the most serious cases, those convicted to be placed on the sex offenders register
Ms Martin started the campaign to change the law after two men took a picture up her skirt while she was at a concert in London's Hyde Park last July.
Police said they were unable to prosecute as the picture was not graphic enough because she was wearing underwear.
'I was upskirted at the bus stop'
Debbie was 17 when a man came and sat down next to her at a bus stop, and then started moving closer towards her.
She says: "I was aware something wasn't quite right, but every time I turned around he pretended to be looking out towards the road where the bus was coming from.
"You don't always have the confidence to say something, so I stood up and walked away.
"But when I turned around to look at him he was holding up his mobile phone. It was a video of my bum - he had been trying to video up my dress."