THE mission to strengthen Scotland's place in the Union will become "so much easier" if a Brexit does not boost support for independence, according to David Mundell.

Writing in the Scottish Daily Mail on Friday, Mundell, who was replaced as Secretary of State for Scotland on Wednesday, said new Prime Minister Boris Johnson must now work hard to ensure that a no-deal Brexit does not "cause chaos" and "play into the hands of Nicola Sturgeon".

In a piece for the newspaper, Mundell warned Johnson and his successor at the Scotland Office, Alister Jack against a disruptive Brexit.

READ MORE: David Mundell: ‘I didn’t believe in Brexit enough for Boris'

In his piece for the newspaper, Mundell wrote: "By far the most important thing I have to say to the new Prime Minister and Secretary of State for Scotland is this: deliver a Brexit that works for Scotland and the whole of the UK.

"Do that and the Scotland Office's core mission – to strengthen our place in the Union – becomes so much easier.

"I have set out out my concerns about a no deal Brexit. During the Conservative leadership contest, I continued to highlight the difficulties it would present, especially for Scotland.

"A disruptive Brexit threatens businesses and plays into the hands of Nicola Sturgeon."

Mundell has previously said that despite his disagreements with the new Prime Minister over Brexit – and having previously said it would be "extremely difficult" for him to serve under Johnson – he would have been prepared to stay in government.

Speaking to the BBC, he also refused to say whether he would vote to block a no-deal Brexit if the matter came before MPs in the House.

Writing in the newspaper, Mundell said: "I am prepared to take the new Prime Minister at his word when he says the chances of no deal are a million to one against.

"So I'm not going to accept scaremongering from the SNP and a First Minister who has consistently craved a no-deal Brexit in a bid to cause chaos and boost support for independence.

"But the new Prime Minister must work hard to ensure that does not happen.

"Having listened carefully to everything he has had to say over the past few weeks, I'm hopeful.

In a joint letter to Johnson this week, Scottish First Minister Nicola Sturgeon and Welsh First Minister Mark Drakeford said that it would be "unconscionable" for the UK to leave the European Union without a Brexit deal.

They said that such an approach would have "catastrophic consequences".

READ MORE: Nicola Sturgeon's letter to new Prime Minister Boris Johnson