The FDA has spoken out against criticism of HMRC civil servants, relating to the Google tax settlement announced this week.
General Secretary Dave Penman said: "The bottom line is that HMRC officials can only work within the law.
"Governments and politicians of all colours are vulnerable to lobbying and accusations of being anti-business when it comes aggressive tax legislation. Tax officials are not.
"However convenient it is for politicians to use civil servants as political pawns, if Ministers are serious about further tackling multinationals, they need to provide tax officials with the legislation and resources to deliver the results they seek."
He added that "tax enforcement requires a continued investment in HMRC if it is to unravel the complex avoidance strategies of multinationals, and the many millions of pounds that these companies invest in big accountancy firms to support their strategies.
"Underpaid civil servants have been working tirelessly on behalf of the public to ensure that everyone - from multinational corporations to individuals - pays the correct amount of tax as the law requires.
Penman also highlighted how HMRC has demonstrated that investment in highly-skilled public servants delivers results:
"During the previous parliament HMRC achieved record-breaking revenues of more than £517bn, with compliance yields up by more than 43% since 2011/12. All of this was achieved whilst meeting Government demands to cut resources by around 25%."
Penman's comments were reported by Civil Service World: Civil servants "unfairly criticised" in Google tax row, says the FDA's Dave Penman
Read the FDA's press release