BRUSSELS — European officials investigating whether Apple, Amazon and other companies received sweetheart tax deals from Ireland and Luxembourg will not take action as soon as expected, the European Union competition commissioner said Tuesday.

The commissioner, Margrethe Vestager, has proceeded with alacrity since taking over in November. She has already announced formal antitrust charges against Google and the Russian energy giant Gazprom, and the companies could face huge fines and orders to change their business practices.

But Ms. Vestager said she was no longer on track to make a decision by late spring in the tax cases, which include an inquiry into Starbucks and a unit of the car company Fiat.

There was “an ambition to do all four cases before the end of the second quarter,” Ms. Vestager said after giving testimony at the European Parliament to a committee looking into tax issues. “It is now obvious, with the problems that we’ve been having to get information, this is not possible.”