The FAST Party deputy Tuala Tevaga Iosefo Ponifasio told RNZ that there's no doubt his party is now the government.
He said they were forced into holding Monday's swearing-in ceremony outside parliament.
"According to the constitution, the head of state is supposed to swear in, and if not the head of state then it will be a council of deputies. But none of those were available. They didn't want to be part of this," he said.
"So as far as we're concerned, we formed the government within the 45 legal days and we've done the swearing in and we do have a government."