A plan to give MPs exclusive use of an NHS clinic has sparked claims that they are getting "priority treatment".
The consultations are paid for by Parliament
The public will be barred from the GP health centre in Westminster for three 90-minute sessions a week so that MPs and peers can attend.
Public funds are to be used to reserve the clinic - and those attending given aliases to "ensure confidentiality".
However, Liberal Democrat MP Bob Russell said: "It's another example of politicians' double-standards."
The scheme has also met opposition from the British Medical Association, which questioned why politicians required extra measures to protect confidentiality.
"If MPs think patient confidentiality is being breached, they should try to protect all patients," said a spokesman.
There is already a health service within Westminster in place to help MPs, peers and other workers, who are often registered with GPs in their constituencies, hundreds of miles away.
There are two occupational health doctors, two nurses and even emergency equipment to tackle heart attacks.
The new scheme would involve slots at the nearby Victoria Health Centre booked for them by one of the nurses.
On the quiet
A letter to MPs said: "You will be asked for an alias of the same sex and approximately the same age when you first register.
"This will be used on all pathology/blood specimens."
Labour MP Dr Ian Gibson said: "I am not aware of any demand for a special GP service."
The Patients' Association is also against the move.
"Why should they get priority treatment?" asked a spokesman.
Liberal Democrat MP Norman Baker told the Independent: "The answer is to get the health service in a satisfactory state where eveyone gets good treatment, not just the privileged few."