Speaking on Daily Politics, Mr Halligan warned further talk of delays or a second referendum would have a negative impact on the UK’s credit rating.
The UK lost its AAA rating after the Brexit vote and concerns have been raised that a similar scenario to the two Quebec independence referendums, held over 15 years, could occur.
Mr Halligan said: “I am actually pretty bearish for this year because the longer the political classes strings out this slow motion Brexit madness, the more business incentives to invest will be dented.
Liam Halligan said UK's credit rating could be further affected
That’s going to hit our credit rating
“For the most part, practical business people in small businesses and large, whatever they were saying on the airwaves, realised once Brexit had happened that we should just get on with it and it wasn’t really going to affect us all that much.
“But If they see the political classes making a complete car crash out of this, spreading economic uncertainty over the next five to ten years, getting the UK into a Quebec-style never-endum if we have a second referendum. That’s going to hit our credit rating.”
May's Brexit speech: World reacts LIVE
Tue, January 17, 2017
Politicians and celebrities tweet their reaction as Theresa May unveils her 12 point plan for Britain leaving the EU.
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President of the European Council, Donald Tusk tweets his frustration.
Sitting next to him on the programme was Labour economist David Blanchflower, who backed the comments.
Mr Blanchflower chipped in and said: “That’s the first time I’ve ever agreed with everything he’s said. Ever!”
Financial services company Standard & Poor’s downgraded both Britain and the European Union’s credit rating to AA following the Brexit vote.
But in first estimates, Office for National Statistics figures show UK GDP smashed expectations to expand by 0.6 per cent in the final three months of 2016.