This will enable the election of his successor to take place at the 2012 Congress in September and for an appropriate hand over period.
Barber said: "I have decided that this is the right time to make a change in my life. I have been enormously privileged to work at the TUC since 1975, and the end of the year will mark the ten year point since my election as General Secretary.
"The TUC has always been a powerful voice for the millions of ordinary people who depend on trade unions to better their lives and there is so much of our work over the years in which I take great pride. But I have every confidence that under new leadership the TUC can go from strength to strength.'
TUC President Paul Kenny added: "Brendan has made an immense contribution to the trade union movement and has been one of the most successful TUC general secretaries. I hope he will continue to make a huge contribution to the movement after he leaves the TUC. He will be duly honoured by affiliates at the Congress."
Under the rules of the TUC each affiliated union is entitled to make a nomination for the position of the general secretary. In the event of more than one candidate being nominated an election is held at the annual Congress with each union's vote being cast based on its total membership. The closing date for nominations will be 9 July.
Brendan Barber became General Secretary-elect in December 2002, and formally took up the position in May 2003 when John Monks left the TUC to become General Secretary of the ETUC.
He first joined the TUC in 1975 and held a number of posts in the TUC organisation, and press and information departments, before serving as deputy general secretary from 1993 until his election as general secretary.
