Berlin- A former state premier who was a prominent minister at federal level quit Germany's Social Democrats (SPD) on Tuesday after receiving a reprimand over critical remarks that "breached party solidarity."

Wolfgang Clement ended 38 years of membership in the centre-left party that co-rules in Berlin with Chancellor Angela Merkel's conservatives after calling the rebuke "inappropriate and wrong."

The outspoken former minister, had outraged many within the party by publicly questioning the energy policies of the SPD leader in the state of Hesse, Andrea Ypsilanti, just days before a closely-fought election in January.

Ypsilanti narrowly lost to Merkel's Christian Democrats (CDU), leading to criticism that Clement's remarks had cost her victory.

Clement, who as economics and labour minister under former SPD chancellor Gerhard Schroeder helped pushed through unpopular pro-market reforms, initially offered an apology for the strong emotions his comments had raised, but stood his ground on the issue.

The SPD in his home state of North Rhine-Westphalia instituted measures to expel him for breaching party solidarity, but the party's mediation committee on Monday issued an admonishment instead.

Clement said in a statement Tuesday that the party's action violated the principle of free of expression.

In earlier remarks, the former premier of North Rhine-Westphalia and "super minister" in the Schroeder cabinet in the years 2002-05 said he had not sought to undermine the Hesse SPD.

But he insisted Germany could not renounce nuclear and coal-fired power stations, as called for by Ypsilanti.

Clement left politics when Schroeder lost office at the end of 2005, taking a senior post with power generation company RWE. He is closely associated with Schroeder's Agenda 2010 programme, which was never popular with the SPD's left-wing. (dpa)