Penistone West Coun Hannah Kitching told the Chronicle she understood the seven councillors now seated on the local authority is the largest representation the party has ever had in the Labour-dominated borough.
It now also has three councillors in one ward, for what’s thought to be the first time in history.
Barnsley's local elections were postponed last year, owing to the pandemic, but parties fielded bumper numbers of candidates this year - including the Lib Dems who, for the first time, contested every available seat.
And of the 21 seats, they were the party to make the most gains - taking Darton East from Labour, Dodworth from the Barnsley Independent Group (BIG), and Penistone West from the Conservative Party.
The latter of those three becomes totally Liberal Democrat-controlled, after Coun Mandy Lowe-Flello beat Conservative Martin Bancroft, 1,444 votes to 1,172.
“Considering last time when seats were up in 2016 the Lib Dems didn’t stand any candidates - we are delighted to go from that to standing a full slate,” Coun Kitching told the Chronicle.
“And it’s important we did so, in a difficult set of elections across the country.
“We are now the largest opposition party on the council, and therefore the official opposition, although that’s a role we’ve had informally for the last couple of years anyway.
“We appreciate a lot of people in Barnsley don’t agree with Lib Dems’ national politics.
“It’s clear a lot of people vote differently locally and sometimes vote locally on national issues, so as Lib Dems we have to work ten times harder than other parties to get elected, and stay elected.
“There have been a lot of Conservative gains around the country, but it’s been business as usual in a sense in Barnsley.
“It’s a Labour administration as is, but now we have official Lib Dem opposition as independent and Conservative councillors continue to be ineffective - apart from Coun Jake Lodge.”
In Darton East, Coun Mat Crisp of the Liberal Democrats won 1,119 votes and took the seat, with Labour's Dave Webster gaining 722 votes in second.
Coun Crisp's success follows up on Liberal Democrat colleague Coun Steve Hunt's 2019 win in the ward - one of seven seats taken from Labour in that election, a famously poor night for the party.
The Lib Dems also unseated BIG leader Phillip Birkinshaw in Dodworth, Coun Chris Wray narrowly winning with 804 votes against Mr Birkinshaw’s 757.
Coun Wray joins Coun Peter Fielding, who ousted Labour’s Richard Riggs in 2019, as the second Liberal Democrat in the ward.
Ahead of the 2019 elections, Coun Kitching was the only Lib Dem member on the council.
“I think people are seeing the benefits of having a Lib Dem councillor,” added Coun Kitching.
“This administration has gone unchallenged, and we know a lack of opposition isn’t good for democracy.
“We now have a team of three people who will fight to give Penistone a louder voice in the town hall.
“It also means we have three Lib Dem councillors on the Penistone Area Council that has previously been Conservative-controlled.
“Residents of Dodworth, particularly around Pogmoor, Gawber and Higham, are really quite disgusted with what the council have done in destroying Penny Pie Park.
“But where people are disappointed where plans have gone through, they know Coun Fielding and his team have done everything they could to hold the council to account - particularly in adhering to things promised such as noise insulation for those nearby.
“More robust opposition is better for everyone.
“Making sure that the wards we hold, we do so with three-out-of-three councillors, is always our priority.
“But I think the other wards’ results demonstrated quite clearly that people are fed up with their Labour councillors, with some very small margins and coin flips, and maybe those residents are now thinking they need a strong Lib Dem voice to fight for their communities.
“Conservatives, independents, Greens, have all proven they can’t do it.”