SCOTLAND’S police and prosecutors are unable to properly prepare for Brexit because of an “unacceptable” lack of clarity from the UK Government, Humza Yousaf has said.

The Justice Secretary insisted there remain “no answers to basic questions” on security and judicial co-operation with the European Union, adding: “The clock is ticking and this is becoming increasingly urgent.”

It came as the SNP’s Westminster leader urged Theresa May to put staying in the single market and customs union back on the table and ignore the “Brexit ultras” in the Tory Party.

With 200 days until the UK’s scheduled exit from the EU, Ian Blackford said the idea of crashing out without a deal "should not be entertained by anyone with a modicum of good sense".

Mr Yousaf urged the UK Government to publish plans for what will happen to measures such as the European Arrest Warrant in the event of a no-deal Brexit.

He said: “We rely on measures like the European Arrest Warrant without which, for example, we might not have been able to bring a number of high-profile criminals to justice.

“This government has been consistently clear on the importance of safeguarding the close co-operation which Scottish police and prosecutors enjoy with their EU counterparts.”

He added: “We are working with our law enforcement agencies to plan in case these co-operation arrangement fall away. With no answers to basic questions, this planning is complex and challenging.”

Since 2011, more than 760 people have been subject to court proceedings in a Scottish court after being arrested on a European Arrest Warrant.

Following a violent attack and murder in Edinburgh in January 2012, one suspect was arrested in Poland within five hours of a warrant being issued.

In 2009, Marek Harcar, a Slovakian national, was jailed for the murder of Moira Jones after being arrested under the system.

Earlier this year, a Scottish Government paper suggested criminal fugitives from other European countries may be able to hide in Scotland after Brexit.

It said police and prosecutors face “complex and far-reaching” challenges in tackling cross-border crime after the UK leaves the EU.

Officials called for existing links to be maintained in order to combat criminals – including protecting access to Europol, the EU’s law enforcement agency.

Mr Blackford said remaining in the single market and customs union represented the “least worst option”.

He said: "What the Prime Minister must not do is listen to the increasingly frenetic noises coming from the Brexit ultras on the government benches.

"While Boris Johnson might be trying to stake a claim to the Tory leadership – an unconscionable prospect – his vision for Brexit would result in significant loss to our economy, jobs thrown on the scrapheap and businesses going bust."

The SNP's 35 MPs could be crucial in any cross-party bid to push Mrs May to accept a Norway-style soft Brexit.

Scottish Liberal Democrat leader Willie Rennie called on Nicola Sturgeon and Scottish Labour leader Richard Leonard to throw their weight behind a second referendum on the final Brexit deal.

He said: "Brexit is unfolding in the most chaotic fashion possible. This is not at all what the Leave campaign promised.

"Now that the facts of Brexit are becoming clearer, it's time for Richard Leonard and Nicola Sturgeon to get their parties off the fence.

"We cannot let Brexit end up as a hard right stitch up. We need a People's Vote and the chance to exit from Brexit."

Scottish Labour's Brexit spokesman Neil Findlay said: “The shambolic handling of the Brexit negotiations so far is more about the chaos at the heart of the Tory party than securing an agreement that works for the people of the UK.

"If Theresa May cannot get her proposals through the commons she must call an election. Labour would deliver a jobs-first Brexit which means a customs union with the EU and tariff free access to the single market.”