Stephen Hardwick, director of communications for HM Revenue and Customs, said Twitter would be a "supplement" to calling helplines. But Mr Hardwick said people should not tweet any personal data.
He apologized pised for long waiting times on HMRC's phonelines and promised more staff for an expected spike in self-assessment calls this month.
When HMRC suggested using its new @HMRCcustomers Twitter account for some queries, Labor MP Margaret Hodge, who chairs the Commons Public Accounts Committee, said the idea was "laughable".
She added: "No customer based service should tolerate such a poor service and both ministers and senior management should simply sort this out."
Conservative MP Mark Garnier said he was unable to think of even a simple tax query which could be expressed within Twitter's 140 character limit, while shadow Treasury minister Shabana Mahmood said it "beggars belief" that the government would encourage people to "publicly tweet about their tax affairs".
But Mr Hardwick told BBC Radio 4's Today programme: "We are serious about the use of Twitter as a supplement to going online and using the telephone.
"What we don't want people to do is to give us any personal details. "It's a very useful social media device to get guidance, to help point people to where they can get information online.
"It's a pilot, it is starting small, but the whole point of social media is you answer a question once and hundreds or thousands of people can see the answer, rather than answering the phone to all of those people asking the same question."
HMRC figures show that average waiting times for its contact centre telephone queues reached 10 minutes and 53 seconds in September - more than double the five minutes and 21 seconds recorded at the same point in 2013.