The text of Vince Cable's letter is below:
Dear Nick,
I am writing to offer my resignation in my role as Deputy Leader of the Liberal Democrats.
It has been an honour to serve as the Deputy Leader of our party. However, in joining the cabinet I have taken on many new challenges and responsibilities and it is right that I focus wholeheartedly on the job in hand.
These are exciting times to be a Liberal Democrat, and despite all the challenges we face we have a real opportunity to change Britain for the better. There are great opportunities for the party alongside our working in coalition.
I wish my successor all the best in what is a rewarding and important role.
Yours ever,
Vince Cable
Commenting, Liberal Democrat Leader Nick Clegg said:
"Vince has been a fantastic Deputy Leader during an exciting time for the party. I look forward to us continuing to work together in government."
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