Overcrowding of Gypsies and travellers living under the Westway has led City Hall to demand west London councils find space for new pitches.
The site, on the border of Shepherd's Bush and North Kensington, is looked after by the boroughs of Hammersmith and Fulham and Kensington and Chelsea.
It has 20 pitches, each designed for one extended family with two caravans - but there are 35 extended families living on the site.
A report called the Gypsy and Traveller Accommodation Needs Assessment (GTANA), produced by the Greater London Authority, recommends that 18 new pitches are needed - 12 for Kensington and Chelsea and six in Hammersmith and Fulham.
A council report to the Westway Travellers Site Advisory Group stated that 'the area of wasteland next to the site could offer potential for additional pitches', but added that they 'may wish to consider if there are any other suitable sites for Gypsies and travellers in the borough'.
A spokesman for the Westway Development Trust said: "The wasteland is the size of a couple of desks. Even if you rearranged the whole site, you could maybe get one extra pitch on it, max."
The report added that the boroughs are likely to have weak grounds for objecting to the GTANA's recommendations, as the Westway site already accommodates more families than it was designed for.
The GTANA, published in March this year, states that accommodation needed for Gypsies and travellers in London will need to double to meet their needs.
