He is the first opposition figure to head the assembly since the now-disgraced former President Alberto Fujimori took control of parliament and the courts eight years ago.

"This is an enormous responsibility. The time has come to change Congress," Mr Paniagua said on being appointed.

He now finds himself with the much more difficult task of guiding Peru through what could be a tricky transition to fresh elections next April and the inauguration of a new president in late July.

Under Peru's constitution, the presidency passes to the head of Congress, if the president, and the first and second vice-presidents are all unavailable or unfit to govern.

Against all odds, this is exactly what has happened in Peru.

The opposition's ousting last week of Mr Fujimori's ally at the head of Congress, Martha Hildebrand, is now beginning to look very well-timed indeed.

Contrasting style

Valentin Paniagua is a respected lawyer and secretary-general of the centrist Popular Action party.

His career in politics spanning nearly four decades contrasts sharply with that of Mr Fujimori, who rose from the political wilderness to the presidency a decade ago.

The bald, moustachioed Mr Paniagua - whose surname means bread and water - was elected to parliament in 1963.

He has had experience of high office before, having served as justice and education minister in two different governments, as well as president of the now-defunct Chamber of Deputies.

Three years ago, he angered Mr Fujimori by defending three constitutional court judges sacked for ruling that the president's bid for a third successive term was illegal. He did so for free.

Mr Paniagua's first act as leader of Congress was to preside over a vote to reinstate the three justices.