John Barrett enjoyed a majority of 13,600 over his nearest rival
Edinburgh West MP John Barrett has announced plans to quit Westminster at the general election.
Mr Barrett, who holds the Liberal Democrat's second safest seat, said he had "enjoyed every moment" since being elected to the Commons in 2001.
But the 55-year-old said he is not a career politician and that he wanted to take on a fresh challenge.
The party's work and pensions spokesman said he hoped he would also be able to spend more time with his family.
Mr Barrett had a majority of 13,600 over his nearest rival at the 2005 election - making it the second safest seat for the Liberal Democrats in the country, behind former leader Charles Kennedy's constituency.
He met key members of the local party on Saturday afternoon to inform them of his decision.
He said: "Serving the people of Edinburgh West at Parliament has been a great privilege and honour and I have enjoyed every moment.
"However, after over 25 years campaigning, I believe the time is right to stand down from Westminster."
Mr Barrett added: "I am absolutely not retiring - at 55 years of age and while I am both fit and healthy I feel I have another challenge left in me.
"Another full term at Westminster would take me to 60 when I feel it would be much harder to make a fresh start at something new.
"Much of my work at Westminster has been with the poorest and most vulnerable people in the developing world. I hope to use the experience I have to continue with work in this field in the future."
Mr Barrett said he had never been a "career politician", instead describing himself as a "community campaigner who went to Westminster to serve my local area, not to further my political ambitions".
He said: "I now am looking forward to the next challenge.
"I am still 100% committed to supporting the Liberal Democrats at all levels."
He said he was looking forward to spending more time with his family.
"The only way I know how to do the job is to give it 100% commitment to the job and this usually means working long hours and most weekends.
"As a grandfather of two lovely granddaughters, I would now like to spend my weekends with them instead."
At the 2005 general election Mr Barrett polled 22,417 votes.
The Tories, who came in second, polled 8,817, Labour had 8,433 votes, the Scottish National Party had 4,124, the Greens had 964 and the Scottish Socialist Party polled 510.