Greece's opposition leader has promised sweeping changes to the economy at a time when the country is slowly back from the brink of an economic collapse.

Ahead of a general election later this year, the leader of the opposition party New Democracy has vowed to restore market credibility during his first year in office. In an exclusive interview, Kyriakos Mitsotakis told CNBC that he wants to bring down taxes for domestic and international businesses in what he described as an "aggressive and comprehensive tax reform."

"This is something we can deliver within the first month (in office)," Mitsotakis said.

His proposals include a plan to bring down the corporate tax rate to 20 percent in two years. However, the current government is also trying to make Greece more attractive to businesses by gradually lowering the corporate tax rate from 29 percent in 2018 to 25 percent in 2022.

"We will also be sending a very clear signal to the capital markets that we mean business. I have committed myself to be able to take Greece back to investment grade within 18 months."

On the back of Greece's financial crisis, which began back in 2009, the country has lost its investment grade from the three major credit rating agencies.

The mandate of the current left-leaning Syriza government ends in October, meaning that a general election is looming. Opinion polls suggest that if the election were to take place now, the conservative party New Democracy would win with about 37 percent of the votes. Syriza would come second with about 26 percent.

The Greek economy is at a turning point having ended nearly 10 years of external financial help last August. The country is no longer part of a bailout program and 2019 is expected to be the third consecutive year of growth at about 2.2 percent.