The Middlesex flag should be flown outside Hounslow Council's HQ as a reminder of its county links, say Tory councillors.
Hounslow was part of the County of Middlesex administrative district until 1965, when the capital expanded with the formation of the Greater London Council.
Most of Middlesex was swallowed up by Greater London and the now extinct county lives on largely through the names of Middlesex County Cricket Club, West Middlesex Hospital and other organisations.
However, the county's advocates, including astrologer Russell Grant, point out that its history stretches back to Anglo-Saxon times and it still exists as a region, albeit one with no administrative powers.
As Labour-controlled Hounslow Council prepares to celebrate the London borough's 50th anniversary, opposition councillors are keen to literally fly the flag for Middlesex.
They want a flag bearing the three seaxes (short, notched swords) of the county crest to be flown permanently outside Hounslow Civic Centre, alongside the Union Jack.
Hounslow Conservative Group leader Peter Thompson said: "Local government secretary Eric Pickles has encouraged local councils to be proud of their local counties and fly their county flag as well as celebrate the date their counties were established. I call on Hounslow Council to follow suit."
His words come after councillors agreed to erect a second flagpole outside the Civic Centre, in Staines Road, to fly the flags of various countries beside the Union Jack on their respective national days.
Conservative councillors were upset that the Middlesex county flag was omitted from the initial list, with no plans to fly its standard even on Middlesex Day, which is celebrated on May 16.
A council spokesman said: "The council has no plans to permanently fly the Middlesex county flag at the Civic Centre. Only the Union Jack and borough flag will be flown permanently, as agreed in the flags policy."