Philip Hammond, who stepped down as Treasury chief before Boris Johnson became prime minister, said the government is making demands that are bound to derail talks with the European Union because they are unacceptable to the bloc. Writing in the Times of London, Hammond said Johnson had moved from a tough negotiating stance to a "wrecking" one by insisting on changes to the withdrawal agreement hammered out over the past two years.

"The unelected people who pull the strings of this government know that this is a demand the EU cannot, and will not, accede to," he said. "Not just because they will be stubborn in their defense of the single market (although they will) but because the fragility of their own coalition of 27 means that any attempt on their side to reopen the package would see their unity collapse."

Hammond also criticized the government for perpetuating the "myths" that the British people voted for a no-deal Brexit and that leaving the EU without a negotiated settlement would be painless.

During the 2016 referendum on EU membership, voters were told that a deal to protect Britain's trade with the bloc would be easy to negotiate, Hammond said. He added that "all credible economic analysis" shows that the costs of leaving without a deal would far outweigh the benefits.

"It's time for our government to demonstrate a commitment to a genuine negotiation with the EU to achieve a deal that will maintain Britain's trade with its nearest neighbors, protect British jobs and ensure our future prosperity," Hammond said.