A Conservative MP has told the House of Commons he is a user of the popper recreational drug and a ban on its supply would be "fantastically stupid".
Ex-minister Crispin Blunt said users of the drug were "astonished" by talk of a ban and respect for the law "would fly out of the window" if it happened.
Supplying the drug, which is popular with gay men, could be outlawed under the Psychoactive Substances Bill.
MPs have rejected calls to exempt poppers from the legislation.
Following a debate in the Commons, they voted by 309 to 228 against the move.
The government wants to crack down on the sale and use of so-called legal highs, psychoactive substances chemically designed to mimic drugs that are already banned. Some 18 deaths in England and Wales in 2014 were linked to so-called legal highs.
But plans to ban the supply of poppers as part of the legislation have caused controversy.
Poppers, the name given to a group of chemicals called alkyl nitrites, are normally sniffed from a bottle producing a short head-rush. They are used recreationally and are often referred to as a "party drug".
During a debate on the bill in the Commons, Mr Blunt - who is the uncle of actress Emily Blunt and is a former prisons minister - said he would be "directly affected" by the ban.
"There are sometimes that something is proposed which becomes personal to you and you realise the government is about to do something fantastically stupid and in those circumstances one has a duty to speak up," he said.
"I use poppers. I out myself as a user of poppers. I am astonished to find it (the government) is proposing it to be banned and frankly so would many other gay men."
Mr Blunt, who came out as gay in 2010, said the drug had been used for decades and a ban would "simply serve to bring the whole law into disrepute". He warned that banning it would "drive supply underground into the hands of criminals" and increase the use of Class A and Class B drugs.
He later told BBC Radio 4's PM programme that he had not suffered any adverse affects from using the drug and there was no "serious evidence" that it posed such a risk. "I think it was the most powerful argument to make and I didn't want to be a hypocrite," he said of his Commons statement.
Personal possession of poppers will not be criminalised as a result of the proposed legislation but there would be a blanket ban on their production, supply and importation, and the police would be authorised to shut down websites selling them.
Critics say this has not been thought through, pointing to a report by the Advisory Council on the Misuse of Drugs which concluded that their misuse is "not seen to be capable of having harmful effects sufficient to constitute a societal problem".
Labour spokeswoman Lyn Brown told the Commons that she had heard that use of the drug "enhances sexual experience".
The shadow Home Office minister said her party supported the government in tackling "the scourge of these dangerous substances" but opposed a specific ban on poppers, saying they had been in use for 30 years and no government had sought to ban them.
"I am greatly disappointed the government has chosen not to place poppers on the exemptions list," she said. "I do believe this will undermine the bill and place popper users, particularly men who have sex with men, at greater use of harm."
Home Office minister Mike Penning assured MPs that a ban on poppers would not permanently take effect without a further review of the evidence, initially by the Medicine and Healthcare Products Regulatory Agency and then by an independent expert.
The review would report by the summer, with a decision to be taken jointly by the Home Office and Department of Health, he told MPs.
"I think that is a compromise," he said. "I think I have listened extensively. I know this is going to be difficult for individuals. I fully respect individuals' views bit I hope everyone in the house respects that I am trying to do the right thing to protect people."
But Mr Blunt, who survived attempts to deselect him in 2013 by members of the Conservative association in his Reigate constituency, said the government could find itself in the strange position of banning the supply of poppers in April and then "unbanning" them later this year.
The likely effect of this, he added, was that users of poppers would end up "stocking up".
David Raynes, from the National Drug Prevention Alliance, said he was surprised by Mr Blunt's intervention.
"Poppers are not an innocuous substance," he told PM.
"The government's own website talks about deaths.
"It talks about heart problems and talks about eyesight problems.
"If people in important positions in public life speak about these things, they are bound to affect the culture and indeed may encourage young people to use them.
"He has had months to make his representations.
"And I deplore the fact it has been done so late in the day and so noisily."