The Lib Dem leader was subject to a scathing attack during his appearance on BBC Two’s Daily Politics on Tuesday.
Coburn insisted voters were turned off by his party’s anti-Brexit stance and said they were “not interested” in the party any longer.
She said: “While I accept you are wanting to be clear where you stand on that particular issue [Brexit], how can you, I say again rebuild in those parts of the country where they rejected Brexit.
“Even in Cornwall for example, had a lot of EU money, [but] they’re not interested in it and you’re making it front and centre.”
BBC TWO/Daily Politics
Jo Coburn bashed Tim Farron for saying the Lib Dems were having a comeback
You are clawing back a few seats here and there but in terms of a resurgence, a big breakthrough, it’s not happening
But Mr Farron insisted it had performed well by-elections since Brexit.
“That’s clearly not the case because if you look at the real elections that have taken place in Cornwall alone since the referendum, four by-elections four Lib Dem gains,” he said.
Coburn probed further and asked about the total number of councillors the Lib Dems now had in total.
“In total, you tell me – 31 more than we had at the time of Brexit, just shy of 2,000 I think?” Mr Farron replied.
Remoaners Club: These people hate Brexit! Mon, January 16, 2017
Remainers are finding it hard to accept Brexit.
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Sarah Olney's by-election win in Richmond Park was hailed as one the party's biggest successes
Coburn dug deeper and asked: “Well it is, it’s about 1,810… how many did you have back in 2010?”
The party leader admitted his party “probably had about 4,000” in 2010 before Coburn blasted him for claiming there was a “resurgence”.
She said: “Right, you say it’s a resurgent Liberal Democrat party, it’s not resurgent is it?
“You’re clawing back, of course, I’m not wanting to deprive you of those wins, but you are clawing back a few seats here and there but in terms of a resurgence, a big breakthrough, it’s not happening.”
However, Mr Farron refused to back down and said his party’s performance since the Brexit vote was “astonishing”.
He replied: “All of that’s correct but I can’t affect elections that have gone by, you can only win what’s in front of you.
“If you look at the by-elections since the referendum, it’s actually astonishing, 31 gains I think. Labour Tories and Ukip all losing seats… there is no pattern except the Liberal Democrats gaining seats everywhere.”