The Home Affairs Select Committee, chaired by Labour MP Chris Mullin, has been investigating freemasonry in the police and judiciary.
In a letter to Pembrokeshire CC requesting information about membership of the masons, Mr Mullin said: 'Local government is one area in which concerns have arisen.'
Pembrokeshire set up a register of members' interests which includes membership of the freemasons when it was set up in shadow form in 1995. It is thought to be the only council in the UK to have done so.
Of 60 members, 11 - all Independent - have declared they are freemasons.