During their combative, often bitter rivalry, the former Mayor of London, Ken Livingstone, has fallen out with Mayor Boris Johnson over buses, Tube fares and policing the streets.
Now the cost of visiting central London's Shard, the English capital's latest tourist attraction, is becoming another bone of contention.
Livingstone has called on his successor to subsidise trips to London's tallest building to ensure the original vision of public access to the tower is guaranteed.
The Shard's viewing floor opens on February 1 with the cheapest adult tickets at £25 ($47.60), if bought online, £30 if bought in person and £100 for immediate, unbooked entry. A child's ticket costs £19. The former mayor believes the charges will price many would-be visitors out of a trip up the tower as they outstrip entry fees for the Eiffel Tower (£12/$23), Empire State Building (£16/$30) and the Leaning Tower of Pisa (£14/$26).
The view from the Shard is also considerably more expensive than other London attractions. The cheapest ticket for the London Eye, the giant Ferris wheel on the south bank of the River Thames, is £17.28 ($33), while the Tower of London is £18 ($34) but there is a family ticket at £47/$90.