"Many of the new poor became so during April, because food prices last month rose by 17.7 percent," he said in a televised statement.
BBC South America correspondent Tom Gibb says the crisis is easily visible on the streets of Buenos Aires, where people sleep out in the parks, queue outside restaurants for leftovers and rummage through garbage to try to eke out a living.
Mr Del Bello described the increase in numbers of poor just since April as dramatic, with almost two million people falling below the poverty line in the space of a month.
He blamed this on the increase in prices of food and other basics by more than 35% since December.
Our correspondent says the suburbs surrounding Buenos Aires are some of the worst hit but the poorest areas are in the north of the country, where almost two-thirds of the population are now living below the poverty line.
Legal reforms
Earlier on Friday the Argentine Government won a small victory in its battle to meet conditions imposed by the International Monetary Fund (IMF).
After an angry day in the country's Congress on Thursday, the government gained partial support for legal changes demanded by the IMF before it releases economic aid.
The lower house eventually passed a measure to amend the country's bankruptcy law, but not before a brawl had broken out among legislators.
The bankruptcy law has been criticised by the IMF because it favours the rights of debtors over creditors.
President Eduardo Duhalde is desperate for speedy approval of changes demanded by the IMF to win billions of dollars in foreign aid.
Economic woes
Argentina's economy has been in the doldrums for several years and reached crisis point last December when mass protests hit the streets.
Argentines have been prevented from accessing their savings and nearly half of the population lives in poverty.
At the end of April, the country appointed its sixth economy minister in 12 months.
Free-market economist Roberto Lavagna became the new economy minister after Jorge Remes Lenicov was forced out of office.
The Argentine Congress had refused to back Mr Remes Lenicov's plan to convert savings into bonds.