The Speaker of the House of Lords was accused of a "downright frivolous" attitude to public money after she ran up a £230 bill keeping a chauffeur-driven car waiting for four hours while she enjoyed a night at the opera.
A return trip by taxi from the Houses of Parliament to the Royal Opera House a mile away should cost about £20 or less than £5 by Tube.
Instead, Baroness D'Souza travelled the short distance in an E-class Mercedes to spend the evening watching Benjamin Britten's Gloriana with a Russian dignitary.
Her driver waited with his car for four hours to take her back to her residence in Westminster, with the taxpayer picking up the £230.40 tab.
Meanwhile, the taxpayer was another £269.75 out of pocket when Lady D'Souza went to lunch with the Japanese ambassador at his residence in Kensington.
Her car and its driver waited four-and-a-half hours for her to emerge from the building three miles from Parliament. A return taxi fare would have been about £30.
Details of her expenses, which followed the freedom of information request by the Press Association, also showed she spent nearly £26,000 on a 10-day trip with three officials to Japan, Hong Kong and Taiwan.
A spokesman said: "The Lord Speaker usually drives herself to events she attends as a representative of the House of Lords. However, at events she has attended at high-profile venues the security requirements of the hosts often require she is brought in a car which must also wait for her departure."