Britain may have to rethink the decision to leave the EU if the government is unable to strike a Brexit deal with Brussels, a former head of the civil service has said.

Bob Kerslake said the consequences of a no-deal exit would be so serious that the UK parliament would have to consider whether it could allow it to go ahead.

Lord Kerslake, who has been advising Labour on preparing for government, said that at the very least the article 50 process – under which the UK is set to leave the bloc on 29 March next year – would have to be paused.

In those circumstances, the European commission would almost certainly insist on some “re-examination” of the original decision to leave, he said.

His comments came as the government prepares to publish a series of technical notes on preparations for a no-deal Brexit across dozens of areas of British life, from farming to financial services.

Kerslake said the measures were “too little, too late” and that the government had not allowed itself enough time to prepare for such an outcome.

He told the the BBC Radio 4’s Today programme: “The consequences of a no deal would be so serious as I think parliament would have to seriously consider whether it could contemplate this.

“The question people need to ask themselves is, is this a risk that they think we should be taking?

“If the government can negotiate a good deal, then so be it. But if they can’t and we end up in this position, then we have to reopen the question of whether we go forward with Brexit at all. It is not too late to do that.

“A pause to reflect would certainly be necessary. I think that is a pretty high probability now.

“But I think that pause would need to include – and I suspect this would be insisted on by the commission – some re-examination of the decision itself.”

The co-chairman of the pro-Brexit Leave Means Leave campaign group, Richard Tice, said Kerslake’s intervention was intended to “soften people up” for a delay to Britain’s withdrawal.

“That would be absolutely appalling. People up and down the country would be furious that our civil servants and government have deliberately ignored the will of he people,” he told the Today programme.

“What we have just heard from Lord Kerslake is part of the deliberate negativity from the civil service who are looking to soften people up in order to extend article 50. It is completely unacceptable.”

It was earlier announced that Nigel Farage was to become vice-chairman of Leave Means Leave to spearhead the campaign against Theresa May’s Chequers plan, which critics regard as a sellout.

Writing in the Daily Telegraph, the former Ukip leader said: “It is now beyond doubt that the political class in Westminster and many of their media allies do not accept the EU referendum result.

“It is equally clear to me that, unless challenged, these anti-democrats will succeed in frustrating the result.”