Eluned Morgan said her MEP colleague Glenys Kinnock was an inspiration
Welsh Labour MEP Eluned Morgan has announced she will not seek re-election after 15 years in the European Parliament next June.
She was aged 27 and the youngest MEP when she was elected in 1994.
She said she was privileged to have represented Wales, but wanted to better balance work and family life.
There is speculation that she could return to politics if Welsh First Minister Rhodri Morgan vacates his Cardiff West assembly seat in 2011.
Ms Morgan paid tribute to her Welsh Labour MEP colleague Glenys Kinnock as an "inspiration".
She said: "After 15 years with a constantly punishing schedule in Brussels and Strasbourg, and the huge task of representing the whole of Wales in addition to the need to better balance work and family life, I believe that it is time to hand on this privileged post.
"I am taking one decision at a time. This has been an agonising decision and one that I have not taken lightly.
"I do not intend to make decisions on my future plans immediately."
Former Welsh Secretary and Neath MP Peter Hain said: "Eluned standing down is a big blow.
"As a friend and close party colleague, I hope she will find an appropriate and senior role in Welsh politics in future because she is one of Labour's brightest stars and the party cannot afford to lose her talents."
Another well-known Welsh figure has also just announced that she is stepping down.
At the weekend it emerged that Welsh Assembly Government Environment Minister Jane Davidson will give up her safe Labour seat of Pontypridd in the 2011 election.