The European Central Bank will struggle to fight the next recession on its own, former IMF chief economist Olivier Blanchard told CNBC Monday.

Amid the vast stimulus that the ECB put forward in the wake of the sovereign debt crisis, there are growing doubts on whether the central bank will be able to deploy the same level of intervention whenever the next crisis hits.

"I am nearly sure that the ECB cannot by itself at this point fight a recession, that it will need help, it is fairly obvious," Olivier Blanchard, former chief economist at the IMF told CNBC's Annette Weisbach in Sintra, Portugal.

He explained that the question is not so much the lack of available tools, but more their actual impact on the market.

"They have a lot ammunition, the question is how much it kills, because they can really buy assets in large quantities, but it may at this stage have little effect on the rates, which is what matters in the end," Blanchard added.

The ECB ended its three-year long bond-buying program in December last year, known as quantitative easing. The purchase of government bonds in the euro zone reached about $3 trillion, but the central bank also bought corporate debt and has kept interest rates at record low levels. The bank's rates on its marginal lending facility and deposit facility are at 0%, 0.25% and 0.40%, respectively.