Tunisia in October sold a 5-year Eurobond worth 500 million euros with an interest rate of 6.75 percent.
Tunisia needs around $2.5 billion in external financing in 2019, officials said.
"The finance committee approved the government's plan to issue bonds up to $800 million," lawmaker Marouan Felfel told Reuters. Another lawmaker confirmed the approval.
The timing of the issuance was unknown.
Opposition parties have criticised the government over the size of Tunisia's debt, which hit record levels of around 74 percent of GDP by the end of 2018. They accuse the government of seeking easy solutions through borrowing.
Prime Minister Youssef Chahed said earlier this year that painful reforms must be launched to keep the deficit under control but his plans face strong resistance from powerful labour unions.
(Reporting By Tarek Amara; Editing by Jon Boyle)