To many people, Barbara Harris is a dangerous woman. A maverick "do-gooder" from California, she has been accused of effectively promoting eugenics via the back door by paying for drug addicts to be sterilised.

Despite being lambasted in the media and condemned by health experts in the UK, Harris is visiting cities around Britain looking to launch pilot projects that will help her achieve her goal of reducing "the number of substance-exposed births to zero".

While Harris may have been subjected to savage criticism from the authorities, a significant portion of the public are warming to her views.

The website of Harris's charity, Project Prevention, boasts scores of emails from Britons supportive of her aims, many of whom have pledged donations while expressing anger that the government will not introduce a similar scheme of its own. Typical comments read: "I had to deal with this issue as a teacher and it enraged me. I hope you are successful in the UK and not defeated by the liberal urban elite who seem to dominate our country with their wishy-washy half-hearted solutions to our deep social problems. I have made a donation."

Another, from a child protection solicitor for a county council, adds: "All I want to say to you is thank god for project prevention! Congratulations on coming to the UK. I get tired of hearing about drug addicts' rights while children suffer… I hope to see the success of this project in my everyday work."

Harris has talked up her growing UK support base on Twitter, although backing for her ideals is by no means uniform. Many of the comments on the site and other social networking online platforms are hostile. Some experts are reluctant to condemn Harris outright.

"The problem that Ms Harris is trying to address is a real one," concedes Julian Sheather, the British Medical Association's ethics manager, writing in a personal capacity on the British Medical Journal's blog.

"A small number of drug-addicted women give birth to a succession of drug-dependent children who are taken into foster care. It is by any standards an appalling start in life.

"There is a certain red-necked 'it does what it says on the can' appeal to Ms Harris's response. Her championing the rights of the unborn over the rights of addict mothers also has a certain populist appeal."

However, Sheather warns, Harris's actions raise serious ethical issues. "Even Project Prevention admits the money will almost always go to feed the addict's habit," he notes.

"Would the addiction render consent invalid? Is the payment a coercive means of getting people to agree to a sterilisation they would otherwise not contemplate?"

Since it was founded in 1994, Project Prevention has paid 3,388 people in the US to be sterilised or to take long-term contraception measures. Of these, 1,059 have chosen Depo-Provera, a long-term injectable contraceptive; 1,260 chose tubal ligation – sterilisation – while the remainder have opted for coils or implants. Just under 50 men have had vasectomies.

In the US, addicts are offered up to $300 (£200) for sterilisation. The charity states its objective is "to reduce the burden of this social problem on taxpayers, trim down social worker caseloads, and alleviate from our clients the burden of having children that will potentially be taken away."

Felicia Le May, a former crystal meth addict who opted for sterilisation after having nine children, told the Sun: "At first I was scared, but then I thought, 'I have too many kids already.'

"They've suffered so much through having both parents addicted. I had my children taken away for two years because of my meth addiction. That was the worst time of my life. I didn't want to risk putting any more babies through the same thing."

Her story is typical of those who have sought help from Project Prevention, which was founded by Harris after she adopted four of eight children born to a Los Angeles addict. Harris said that she decided to take action after spending "countless hours watching her children fight through withdrawal".

There have been accusations the charity focuses disproportionately on black people.

It insists it "targets a behaviour, not a racial demographic". Since she arrived in the UK earlier this month there have been reports that a woman was approached near a health centre in Glasgow by three women from Project Prevention who offered her £200 if she agreed to be sterilised. The woman was with her nine-year-old son and was not a drug addict.

However, Harris told the Observer in an email that the story was untrue. "We never approach people on the street," she said, adding: "We never assume someone is an addict, no matter where we go. We approach people asking if they know any drug addicts they can give our info to."

The controversy generated by her visit to the UK this month has focused attention on the risks to children of drug addicts. It is reported that one out of every 264 babies born in Scotland suffers withdrawal symptoms from mothers who use drugs including heroin and cannabis.

In a sign that she is serious about bringing her vision to the UK, Harris confirmed that she is seeking UK charitable status, though there are questions over whether the Charity Commission will approve this given the group's controversial aims. Harris also confirmed she is considering several cities in the UK for potential pilot projects, although she has yet to decide whether she will proceed.

Martin Barnes, chief executive of DrugScope, an independent organisation that examines drug issues, accused Project Prevention of applying what could be "a simplistic, moralistic and exploitative approach to addressing the difficult and complex issue of drug use and pregnancy".

He added: "The welfare of children is paramount, but using cash incentives to often poor and vulnerable women is highly questionable. For many women with drug problems, the chance to become a mother can be life-changing and a powerful motivation to seek help for their addiction and other problems in their lives."

He warned that legitimising Project Prevention could have significant repercussions. "Where should the line be drawn? Women who drink? Women who smoke? Women with mental health problems? Women who themselves have been the victim of abuse?"