A demonstration has been held in Glasgow against the so-called "rape clause" in changes to tax credits.
Reforms of the welfare system which came into force in April mean child tax credits are now capped at two children.
A clause in the new rules means mothers who have a third child as a result of rape can be exempted - but would have to provide evidence to do so.
There has been a political row over the policy, which First Minister Nicola Sturgeon has called "disgusting".
Scottish Conservative leader Ruth Davidson has defended it, saying she wants the UK government to implement the exemption "in the most compassionate way possible".
The Tory leader has faced criticism from a number of politicians, including Ms Sturgeon and Scottish Labour's Kezia Dugdale, over her stance on the matter.
The plan to restrict tax credits for any new claimants to a maximum of two children was announced in the 2015 Budget, and came into force from the start of April.
Women who have a third or subsequent child as s result of rape will still be able to claim tax credits, but will have to demonstrate their "exceptional circumstances" in order to qualify - an exemption campaigners have dubbed the "rape clause".
The UK government's Department for Work and Pensions argues that allowing women to claim tax credits for a third child in specific circumstances is an exception they have made in a "compassionate" way.
However, a large group of psychologists signed a joint letter warning that "the way in which this rape clause is to be administered will cause significant psychological harm".
Protestors gathered in Glasgow's George Square to speak out against the policy.
SNP MP Alison Thewliss, who attempted to force an emergency debate at Westminster over the changes, spoke at the rally.
She said: "Tonight we gather to speak with one voice and send a clear message to this Tory government: 'Scrap the rape clause and two child policy now.'
"The fact that women have to demonstrate in George Square in 2017 against such a barbaric and vile policy is bad enough. What's worse is the wall of silence these women are being faced with.
"Ruth Davidson and Theresa May cannot hide behind that wall of silence much longer. We are not giving up and we will fight this appalling policy every step of the way. We will not rest until our voices are heard and these anti-women policies are consigned to history."
Ms Davidson said Holyrood had the power to create new benefits, saying the Scottish government could use this to offset the two-child policy if it chose to.
She said: "We support the exemptions which the UK Government has put in place on restrictions to child tax credits, and we want to see the UK Government implement them in the most compassionate way possible. That work is on-going.
"The SNP has said it opposes the two-child policy on tax credits, so it now has a choice to make.
"At Holyrood, we now have the power to create new benefits. So the Scottish Government could, if it wanted, propose a new benefit to provide funding for families with more than two children.
"Of course this would have to be paid for, but if the SNP government believes this to be of such importance, then it can act.
"However, if Nicola Sturgeon simply wants to use this to complain about the policies of the UK government - and not act at Holyrood when she has the power to do so - then she leaves herself open to the charge of gross hypocrisy."
Pressure had been building on Ms Davidson to speak out after Ms Dugdale wrote a newspaper column urging her to confront Prime Minister Theresa May about the "barbaric" changes.
The Scottish Labour leader has since written to Ms Davidson asking her to "join with us and condemn this appalling act", saying the clause "should shame every single Tory MSP".
Ms Sturgeon posted on Twitter that the Conservative leader "seeks to defend the indefensible", and called her response "pathetic".
She wrote: "Scottish government spends millions mitigating welfare cuts and will continue to do so. We wouldn't have to if Tories didn't make callous cuts."