Only 35 per cent of Leave voters think Brexit will happen on 31 October according to a YouGov poll.
The UK is due to leave the EU at the end of this month, but the number of Leave voters that think this will happen has fallen by 25 per cent, from 60 per cent, since the start of September.
Of those who voted for the Conservatives in 2017, 40 per cent think the deadline will still be met, while just 26 per cent of the general public agree, down on 45 per cent a month ago.
Confidence that Prime Minister Boris Johnson will get Brexit over the line on Halloween has fallen drastically having originally risen falling his appointment at No 10 in July to a peak at the start of last month.
The dip comes following reports Johnson will obey the Benn Act, which was given royal assent last month forcing the Prime Minister to request an extension to Brexit should no deal be agreed by 19 October.
New proposals over the Irish backstop have also been met with scepticism, with further discussions with EU officials set to continue next week.
Johnson’s attempt to prorogue parliament were also overthrown by the Supreme Court last month – one of a number of blows to the PM’s efforts to force through Brexit.
While the majority of Leave and Conservative voters said a delay to Brexit would not be Johnson’s fault in early September – when confidence it would be delivered on time peaked – the number who think the Prime Minister would be blameless has now risen further.
65 per cent of Conservative voters believe Johnson would not be at fault for a delay, up from 59 per cent, while 64 per cent of Leavers agree, up from 60 per cent a month ago.