David Moreland said there has been a spike in applications on the back of a farcical Brexit strategy from Theresa May and the surge has not slowed down.
He said: “Our membership site completely crashed and we keep on getting applications.”
The most recent data on political party membership put Ukip membership at 21,200 as of April 2018.
Mr Moreland said: “We are well in excess of 23,000 members. A lot of it is people returning to Ukip and people leaving the Conservative Party.”
The reason for the sudden surge is a direct reaction to Mrs May and her Government’s handling of the UK’s departure from the European Union, specifically following the Chequers plan, according to the party chief.
Mr Moreland said: “It’s all to do with Theresa May and her government. It’s treasonous. The people voted Brexit. They voted to leave and the British public don’t feel like enough is being done.”
Over the past two weeks Mrs May’s divisive Chequers plan has resulted in the headline resignations of David Davis and Boris Johnson, stating the Brexit white paper did little to meet the demands of Leave campaigners.
With the Tory Party fracturing Mr Moreland says the Government is not delivering on its promises.
A top Ukip member has said Mrs May’s Chequers plan is to attribute to rising Ukip numbers
He added: ”We just feel let down. When you see what’s happened recently it looks like we aren’t going to fully leave and we will still be controlled by Europe.”
A recent poll from YouGov showed the voting intention for the Ukip party increased from four percent to nine percent after the Chequers meeting.
Voting intention for the Conservatives dropped from 74 percent to 64 percent.
Another explanation for the rise in membership numbers of the Eurosceptic party is the former leader’s possible return to politics.
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Nigel Farage announced after Mrs May hailed the Chequers agreement a success that there is a sense of betrayal.
He said on The Wright Stuff: “I was a businessman who went into politics because I wanted to change things. I thought I had changed things.
“Now I see this woman, the Prime Minister, trying to overturn all of our achievements. If they don’t get rid of her and get back on track then I will, next spring, come back into the front line of British politics.
“I’ll tell you what. If I have to do this again, next time no more Mr Nice Guy.”
Ukip has received more than 2,000 membership applications in the past two weeks
“To put through something like Brexit, to turn the ship of state around by 180 degrees, take back our independence, do these things, you have to actually believe in it.
“Theresa May was a Remainer. She’s not up to the job and if she stays on as Prime Minister we are not going to get the Brexit we voted for. The sense of betrayal in this country will be huge, and I very much hope that she’s out of office before too long.”
Mr Moreland said Mr Farage’s announcement also explained an increase in membership applications.
He said: “People are also coming back because Farage has said he wants to get into politics again.
“He’s still popular among Ukip and people are definitely coming back because of him.”
Between December 2015 and December 2016 Ukip membership declined from 40,000 members to 34,000 and the trend only continued in a steady decline.
Ukip members were the least likely to vote in 2017 General Election and if they did they voted for the Conservative Party as 45 percent of 2015 Ukip voters went to the Tories, according to data from YouGov.
Mr Moreland said: “The political elite think the British public are stupid and they are not. We voted to leave and we woke up and won.
“The Ukip party has suffered or to years and we feel there was deliberate move to get rid of us after the Brexit vote but now that people see what is happening they are coming back.”