In a letter to Nicola Sturgeon about his decision he said his mandate had been to partner her at Westminster but now it was time to move on.
He said in a tweet he would “always be there to help Scotland reach its full potential”.
Mr Robertson lost his Moray constituency in the UK general election last June to Conservative Douglas Ross.
Mr Robertson lost his Moray constituency in the UK general election last June
Thanks to all colleagues and constituents over 17 years of public life. It’s been a tremendous honour to serve as deputy of @NicolaSturgeon and help transform Scottish politics. Look forward to new opportunities but will always be there to help Scotland reach its full potential. pic.twitter.com/S6qznishFe
— Angus Robertson (@AngusRobertson) 3 February 2018
Ms Sturgeon expressed her “immense gratitude” to Mr Robertson, telling him: “You have always been a source of wise counsel and I, likewise, have valued your friendship and support in the work we have taken forward together.”
The SNP leader added: “I know that you are keen to pursue other career opportunities at the moment, and I wish you well in those endeavours, but I hope that we may see you return to front-line politics in future.”
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The letter to Nicola Strugeon reads: “As we have discussed recently, I believeI am no longer able to fully discharge my mandate, which was to partner you as Westminster SNP Leader and as a Parliamentarian representing a rural constituency.
“While it would be my greatest privilege to continue as Deputy Leader, I know you understand that I have to focus on pursuing new career opportunities.
“It is for that reason that I believe it is for others to step forward to seek the support of SNP members for the honour to serve as Dupute Leader of Scotland’s largest political party.
Thank you @AngusRobertson – you have been an outstanding Deputy Leader of @theSNP and a huge support to me personally. You should be very proud of your enormous contribution to our Party’s success. I wish you well and hope to see you back in frontline politics in the future. https://t.co/8F3lACFe1o
— Nicola Sturgeon (@NicolaSturgeon) 3 February 2018
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“I have been tremendously honoured to be your deputy since 2016 and always valued your friendship, professional and personal support, and your inclusive leadership of the SNP and Scottish Government.
“It has been a fantastic time to be involved in public service for 17 years, representing the community I live in and moving our country ever closer to independence.
“To help the SNP become the Party of Government in Scotland has been a personal high point and i am exceptionally proud of all that our Government has achieved.
Ms Sturgeon expressed her ‘immense gratitude’ to Mr Robertson
“I intend to continue supporting public policy development in Scotland as an Advisory Board Member of the Scottish Policy Foundation while working in business, communication and public diplomacy consultancy at home and internationally.
“If I can be of any help in supporting Scotland’s progress and the progress of every person who lives here, I remain as committed as ever to our Party and the cause we both signed up to as teenagers.
“I wish you well as you continue to lead our Party and our country. You can always count on my support as you do so.”
Mr Robertson was replaced as SNP Westminster leader by Ian Blackford after losing his Westminster seat in the General Election.
The former deputy won widespread praise for his performance at PMQs with many political opponents commending his forensic questioning of the Prime Minister.
More to follow…
The former deputy won widespread praise for his performance at PMQs
Ms Sturgeon told Mr Robertson that he had “always been a source of wise counsel” to her.
She added: “Our political and electoral success over the last decade has been nothing short of extraordinary – and the party owes you an enormous debt of gratitude for the personal role you have played in bringing about that success.
“That includes your part in the 2014 referendum which brought the country closer to independence than ever before.”
The SNP leader added: “We remain the preeminent electoral force in Scotland, and the latest opinion polling shows us 17 points ahead of our nearest rivals almost 11 years into office, which is a remarkable vote of confidence from the people we serve. You can be very proud of the part you have played in this success.
“I know that you are keen to pursue other career opportunities at the moment, and I wish you well in those endeavours, but I hope that we may see you return to front-line politics in future.”
More to follow…