GUATEMALA CITY (Reuters) - Guatemala’s top court opened the way on Monday for an investigation of President Jimmy Morales for alleged illegal campaign finances, but Congress will have the final say on removing his presidential immunity and could yet block the probe.

Guatemala's President Jimmy Morales attends a meeting with mayors in Guatemala City, Guatemala, August 29, 2017. REUTERS/Jose Cabezas

The attorney general of the Central American nation and a U.N.-backed anti-graft body said last month that they were seeking to investigate Morales over the campaign financing. Two days later Morales declared the head of the U.N. body “persona non grata.”

Prosecutors will need to win a two-thirds majority in Congress for Morales to be formally investigated and charged.

Prosecutors may have a tough time winning enough support in Congress to strip Morales of his immunity since all the major parties are being investigated.

Morales said in a statement that he has always respected the rule of law and the separation of powers between different branches of government. He has denied wrongdoing in the campaign finance scandal that has tarred all the country’s top parties.

Late last month, Guatemala’s attorney general and the U.N.-backed International Commission against Impunity (CICIG) said they would investigate parties on suspicion of illegal campaign financing during the 2015 presidential election campaign.

CICIG head Ivan Velasquez has said there is evidence that Morales broke the law when he was head of the conservative National Convergence Front (FCN).

Under the leadership of Velasquez, a veteran Colombian prosecutor, CICIG has been a thorn in Morales’ side, investigating his son and brother, and then seeking to remove his own immunity over more than $800,000 in allegedly unexplained campaign funds. Morales has denied any wrongdoing.

Morales struck back on Aug. 27, ordering Velasquez out of the country in a move that provoked international outrage. The nation’s constitutional court ruled against the president, finding he did not have the authority to expel the CICIG head.

Morales won office in 2015 running on a platform of honest governance after his predecessor, Otto Perez Molina, was forced to resign and imprisoned in a multi-million dollar graft case stemming from a CICIG investigation.

The next move by lawmakers will be to vote on constituting a special committee that will decide if stripping Morales’ immunity gets a floor vote.

“I see a favorable scenario for the president because three of the main parties are being accused of the same illegal financing,” said Roberto Alejos, founder of the centrist Todos party that was formed by dissidents from other parties.