Two former Tory HQs are in the running to house an EU "super embassy" in London, but finding somewhere to fly the flag is proving to be a problem.
Smith Square saw three election wins for Lady Thatcher
Smith Square and Victoria Street are among options being considered for a joint office for two sets of EU staff.
But if they are to fly the EU flag at Victoria Street, they would need to rent the whole block, at £3.2m a year.
Tory MEP Martin Callanan said it would mean £1.3m a year being "squandered" on a larger-than-needed building.
London-based European Parliament and European Commission staff are currently housed in two separate buildings.
An internal report on the search for new office space pointed out that, unless the whole building was rented, "permission to fly the EU flag or display other forms of externally visible identification will almost certainly not be given."
It adds that there seems to be "a general attitude in London that where there is a multi-tenancy building, ie more than one occupant, landlords will not allow 'branding' of the building".
A previous deal failed on a property in Tothill Street, central London when the landlord would not allow a plaque to be displayed, the EU flag to be flown, or the offices to be called "Europe House" - in case other tenants objected.
The Conservatives sold 32 Smith Square - the home of many election triumphs, most notably Margaret Thatcher's three victories - to a property developer earlier this year, in a £30.5m deal.
Conservative MEP Mr Callanan said it was "somewhat ironic that the EU wants to spread the gospel of Euro-federalism from a former Conservative HQ".
'Lots of options'
He said Victoria Street would be bigger than needed, adding: "Putting aside for a moment whether we actually need this propaganda machine in London, the prospect of more than a million pounds a year going to waste on this project is horrifying.
"They seem to be obsessed with flying the flag, even to the point of squandering massive amounts of taxpayers' cash."
A UK spokesman for the European Parliament confirmed both offices had been considered, but said no decisions had been taken and they were "looking at lots of options".
He added that wherever the office was, it would have to have some way of identifying itself.