Solomon Islands Prime Minister Gordon Darcy Lilo has ordered an urgent inquiry into hundreds of "ghost teachers" drawing more than one salary.

The Ministry of Education believes there are more than 500 teachers on the government payroll who do not exist.

Mr Lilo says the practice involves teachers who use more than one name and separate bank accounts.

He says it means those teachers have been committing fraud against the state.

The Prime Minister says he was surprised by the extent of the problem, and says if it is proven, the government will deal with them accordingly.

The investigation comes as teachers in the Solomons continue strike action over a pay dispute, which has extended for much of the year.