The council promised last month it had introduced special measures to prevent Travellers pitching up on public space near the 2012 site, but 10 caravans have set up home in a Homerton park amid warnings it could become the next Dale Farm.

A section of fence was removed to allow access onto a disused football field used by dog walkers to let their dogs run off-lead on Mabley Green, off Lea Conservancy Road.

Last month when a convoy of French holiday makers parked 11 caravans on the same green next to the A12 flyover, a council spokesman said Hackney and the other Olympic host boroughs had contingency plans in place to prevent parks becoming caravan sites in the run-up to London 2012.

“We will not tolerate this unauthorised use,” he said at the time.

Johnnie Walker, chairman of Hackney and Leyton Football League, which uses pitches on Mabley Green, believes Travellers may have moved off a site on the outskirts of the authorised site in St Teresa’s Close just metres down the road, where they had been parked illegally for months.

“If the council have taken measures they aren’t visible, and I don’t see how they can unless they have permanent security guards on the gates,” said Mr Walker.

“How can they do it? It’s common land,” he added.

“What’s the point of moving them on if they’re just going to go next door?

“To be honest they didn’t infringe on us in the carpark, but the fact they are there and not been moved is troublesome, because if they allow some to be there, soon they will all get on the bandwagon.

“Setting a precedent is a dangerous thing if it’s not nipped in the bud early enough. You don’t want to turn the marshes into another Dale Farm,” he warned.

Petra Jackson, 47, of Kingsmead Way, who uses the space in Mabley Green to exercise her dog, said the inconvenience made her “sick”.

Gill Brown, community and research worker at the London Gypsy and Traveller Unit in Westgate Street, said the Travellers would not want to make a statement until they knew what action the council was going to take.

Cllr Sophie Linden, cabinet member for crime, sustainability and customer services in a statement: “We have already commenced the necessary legal processes and hope to be able to move them on as soon as possible.”