Martha Lane Fox has quit her role as the Government's UK digital champion after more than three years.
She was appointed in June 2010 to advise the Government on how to encourage more people to get online.
I will focus my efforts on the vital issue of building digital skills.
This is also an area of focus for her digital inclusion charity, Go On UK, which aims to make the UK the most digitally skilled nation in the world.
In her resignation, the co-founder of Lastminute.com did not go into detail about the reasons behind her departure, but vowed to remain a "critical friend" of the Prime Minister from her crossbench seat in the House of Lords.
"I feel it is now time I step down from that role," she stated in her letter.
"As chair of Go ON UK, I will focus my efforts on the vital issue of building digital skills. Go ON UK will, of course, continue to work closely with the newly-created digital inclusion team in [the Government Digital Service department] and I will continue to be a critical friend from the House of Lords."
In response, Prime Minister David Cameron said: "As we shift focus to implementing and designing the services you imagined, I hope you will remain a supportive and challenging voice.
"I am sure your work with Go ON UK will help bring even more people into the revolution you have started and I know the Government Digital Service are keen to work with you to ensure it is the next success."
Her goal as digital champion was to get more people in the UK online, as it is estimated that around seven million people in the country are still unable to use the internet.
