The opposition in Solomon Islands has lodged a motion of no confidence in the government of Danny Philip.
The move follows days of uncertainty within the opposition group over who should be its leader after Steve Abana's resignation.
It chose as its new leader a former prime minister, Derek Sikua, who has now challenged Mr Philip.
Mr Philip and his foreign minister are in Fiji for the Melanesian Spearhead Group summit.
There was substantial instability within the ruling coalition at the beginning of the year when the opposition first considered to challenge the government which was formed after last August's general election.