DAVID Davis has warned Nicola Sturgeon not to use Holyrood to try to block the UK Government’s flagship Brexit legislation because it could create a “black hole” in British law and make it unworkable.

The Brexit Secretary’s warning came as Tory grandee Lord Patten branded Brexit a “dog’s breakfast” and said the country was in a real mess, probably worse than after the Suez Crisis of the 1950s.

Last week, David Mundell, the Scottish Secretary, insisted it would be “incredible” for Holyrood to refuse to back Westminster legislating for Scotland on Brexit as it would ultimately lead to fewer powers returning to Edinburgh from Brussels.

Constitutional lawyers from both governments are currently arguing over whether a so-called Legislative Consent Motion [LCM] is necessary; this is the parliamentary mechanism by which MSPs agree to allow MPs to legislate on matters normally devolved to Edinburgh.

Given the Brexit process impinges on devolved competences, most politicians, including Mr Mundell, believe an LCM would be necessary.

While constitutionally Holyrood has no veto over the Brexit process, if MSPs decided, for whatever reason, not to grant approval, then Theresa May would be placed in a constitutional dilemma: either to try to negotiate with the First Minister over a blockage to the Brexit legislation or ignore the will of Holyrood and push on regardless with all the political ramifications that would entail.

Mr Davis yesterday gave a clear warning about what any blockage to the Brexit legislation, most notably the Repeal Bill which seeks to transfer all EU law into UK law, would mean. Cautioning that any such blockage would leave a “black hole” in the statute book, he said: “If somebody disrupts that, they are taking on themselves the responsibility for making the British statute book, British law, unworkable as we leave the EU. Do they really want to do that? I don’t think so.”

But Tommy Sheppard, the SNP MP for Edinburgh East and the party’s spokesman for the Cabinet Office, said: “If an LCM is required, it is more likely to be passed if the consent of the Scottish Government is genuinely sought. Using a big stick is unhelpful in trying to get agreement. David Davis would have a great prospect of success if he used a different tone.”

A spokesman for the First Minister said: “We will always act in Scotland’s best interests.

“The UK Government has so far not shared the details of the proposed Repeal Bill with ourselves or other devolved governments. We have been clear that powers must not be removed from the Scottish Parliament in this process. A Westminster power-grab would be totally unacceptable.”

In other developments: n Lord Patten said: “Thanks to the calamitous errors of two Conservative prime ministers in a row, who thought they could manage the unmanageable English nationalist right wing of the Conservative Party, we’re in this hell of a mess.”

n Labour’s Jeremy Corbyn suggested the Scottish Government had to have “clear input” into the Government’s Brexit negotiating process.

n Ian Blackford, the SNP’s new Westminster leader, attacked the “shambolic, rudderless” Tory administration and also pressed the PM to involve the devolved administrations in the Brexit talks.

n But Priti Patel, the International Development Secretary, rejected the calls from Labour and the SNP as well as from Justin Welby, the Archbishop of Canterbury, that other parties should be involved in the UK’s Brexit strategy, possibly as part of a cross-party commission, saying: *Jon Trickett, the shadow Cabinet Office minister, indicated Labour could still push for membership of the single market, saying his party wanted Brexit to work for jobs and growth and stressing it was not “wedded to any particular institutional framework”.

*Labour would have won the election if the campaign had lasted a few weeks longer, John McDonnell, the shadow Chancellor, claimed.

Elsewhere, Mr Davis said he was “pretty sure but I’m not certain” a Brexit deal would be done with Brussels while suggesting that he expected the so-called transitional arrangements following the Brexit deal to last up to two years.

The Brexit secretary said part of his portfolio was planning for a bad outcome.

“We cannot have a circumstance where the other side says that they are going to punish you. So, if that happens, then there is a walkaway, and we have to plan for that. Half my job is the invisible job of actually planning for all outcomes, the good, the bad, the whole range,” he added.

But Tom Brake for the Liberal Democrats said: “David Davis inspires about as much confidence as a drunken trapeze artist. But it is the country as a whole that will suffer when he comes crashing to the floor.”

Sir Keir Starmer, the shadow Brexit secretary, added: “Labour has been clear that no deal is not a viable option as it would be catastrophic for British trade, jobs and security. The sooner David Davis realises this, the better.

“Instead of preparing for failure the Government should be putting all their efforts into getting a Brexit deal that works for Britain - that means putting jobs and the economy first and dropping the no deal mantra.”

Today, the Government will publish the details of its “serious and fair offer” on EU citizens’ rights. Mrs May is expected to make a Commons statement.