"We have a problem with commercial debt, which amounts to no less than $20 billion ... we already have a default - de facto, we have it, but de jure we do not," Yuzhanina told the Novyny Live broadcaster.
The Ukrainian parliament may announce a possible tax increase to test the reaction of Ukrainian citizens, she said, adding that the decision is also being considered in the presidential office, but the Ukrainian authorities have not yet decided to make the issue public due to concerns over negative consequences.
"We have a very large gradation of people in our society: those with very high incomes and those on the verge of poverty … We now have more than 50% of Ukrainian nationals below the poverty line," Yuzhanina added.
On Monday, The Economist reported that Ukraine could declare a default as early as in August if the authorities fail to reach an agreement with creditors on debt restructuring, with the deal now appearing unlikely.