His comments were made during a Twitter exchange on July 4, where Cummings was asked whether he regretted anything about the June 2016 referendum outcome. Cummings wrote on Twitter:
Lots! I said before REF was dumb idea, other things shdve been tried 1st. In some possible branches of the future leaving will be an error— odysseanproject (@odysseanproject) 3 July 2017
He said that the government's negotiating strategy was "chaotic" and a "farce," and that Brexit would be a "guaranteed debacle" if Whitehall fails to make substantial changes.
The Vote Leave campaign has not been without its controversy, they famously made a claim that Brexit would allow for an extra US$452 million (£350m) per week to be invested in the National Health Service (NHS).
If Leave MPs don't assert themselves to force MANAGEMENT changes on No10/DEXU, Brexit talks = guaranteed debacle as Ive said for a year— odysseanproject (@odysseanproject) 13 June 2017
Outgoing Liberal Democrats leader Tim Farron said that Cummings had lied to the public. Farron then went on to call for a second referendum.
"Dominic Cummings has let the cat out of the bag. This is the man who slapped the £350 million NHS lie on the side of the bus who is now saying leaving the EU could be a mistake, Tim Farron said.
"These Brexiteers have sold us a pup and lied to the public. This is why I believe the public should be given a say on the final Brexit deal," Farron added.
Dominic Cummings, the man who created the £350 million lie on the side of the bus, admits leaving EU could turn out to have been a mistake https://t.co/TWiFfuHmbo— Tim Farron (@timfarron) 3 July 2017
Cummings' remarks come a day after a poll found that the majority of Brits would vote Remain if the EU referendum were held today.
According to a Survation poll, 54 percent would vote Remain if they were heading to the polls now, while only 46 percent would back Brexit.
A majority (52 percent) voted to leave the EU in the June 2016 referendum, while 48 percent voted to remain.