The borough’s four Liberal Democrat councillors - Hannah Kitching, Peter Fielding, Steve Hunt and David Greenhough - expressed disappointment over the rejection of their budget amendment.
The group sought to have £1.3m ringfenced for the 20mph scheme, which related to all residential streets and school frontages.
However, the proposal did not receive support and the local authority will instead press ahead with its plan to ask every councillor to put forward three hotspots in each ward.
Council leader Sir Steve Houghton said: “The biggest cause of collisions, by far, is driver behaviour and not speed limits.
“Having 20mph limits on every street, by default, would cost well over £20m and that assumes they’re not objected to.
“As we have seen before when we’ve put in speed humps, chicanes or speed indicators, there’s been objections as people don’t want these outside their properties.
“It’s not straight-forward even if we had level of funding required, which we don’t.
“What we should be doing is what we are doing, and that’s looking at where we have serious problems, then prioritising what’s required.
“Every member in every ward has been asked to provide their top three locations where they would like to see improvements, so the commitment is there.
“It’s about getting the right solution for the particular problem. When it comes to schools, we’re more than happy to look at that but without enforcement, problems will continue.”
The rate of motorists sustaining serious injuries when behind the wheel is 59 per 100,000 residents - significantly higher than the national average of 42.6 - and is now the second-highest in the region, with more than 64 per cent involving males.
Speed is thought to be a large factor in the higher-than-average rate, particularly so with young motorists, which has led to multiple areas of Barnsley becoming the subject of resident-led petitions in an effort to reduce speed limits.
Coun Kitching added: “Barnsley’s rates of killed and seriously injured casualties are significantly higher than the national average.
“It has long been clear to us that Barnsley Council do not take road safety seriously - that is demonstrated by the horrifyingly above average levels of road deaths and serious injuries in recent years.
“This is a huge priority for all our residents who want to see commitment to improving road safety at all levels.
“While we absolutely welcome the newly proposed measures including neighbourhood road safety initiatives, these simply do not go far enough or deliver enough investment.
“Research done by the Liberal Democrat group has shown a highly effective way to make Barnsley’s streets safer is to implement 20mph limits in all residential areas and outside all schools.
“Our proposals would have used unallocated capital reserves to fund this scheme in a phased manner over three years, while simultaneously applying for external funding as has been used in other council areas.
“It was disappointing but not surprising that our amendment was rejected.
“What was surprising was the vehemence with which the Labour council argued against evidence-based road safety measures which are working well in other Yorkshire authorities.
“Their reaction to any kind of challenge or opposition is to lash out in anger and fear.
“This is a spineless rejection of proper democratic processes.”
Cabinet spokesman Coun Chris Lamb said the £1.3m figure did not reflect reality.
He added: “Road safety is about so much more than 20mph zones.
“The £1.3m figure seems outstanding value but it’s worthy to note this would be a self-enforcing scheme, so in reality the cost is not anywhere near that.
“What’s been put forward would cost £21m, as the implementation of 20mph zones would require engineering interventions on 727 kilometres of roads.
“I have no doubt the Liberal Democrat members’ concerns are genuine, but the facts should be known.”