More than £1m in fines could be given back to motorists as Ealing Council complies with an order to do a U-turn over two box junctions in Southall.
This week the council was told to pay £750 in costs to a bus company and, depending on a further decision from the Department for Transport, it could be reimbursing even more drivers.
London United Busways had contested 17 tickets handed to it for drivers stopping in two controversial junctions in South Road, Southall.
This week the Parking and Traffic Appeals Service ruled against the council. Enforcement on the two sites has now been suspended.
Campaigner Jim Douglas, who has been fighting to get changes to the two yellow box junctions, which are enforced by cameras, said Ealing has made at least £1m from fines during the 2007/8 financial year.
He said: "I think Ealing have dug themselves into a huge hole.
"If the Department for Transport comes back and says it can keep the boxes as they are, it means every single ticket issued until the date of authorisation, which hasn't been decided yet, is illegal.
"If the DfT says it will not authorise the box junctions, then that will also be an admission that they are illegal and the council will have to issue a refund.
"If nothing else there will be public pressure on the council to give back the money. I don't see how they can't."
Mr Douglas added that a further 65 tickets issued to London United Busways since March could also be quashed.
A council spokeswoman said: "Following Wednesday's judgement, the council has taken the decision to suspend enforcement of yellow box junctions in South Road, Southall, until guidance it sought from the Department for Transport is received.
"The yellow box junctions were put in to respond to concerns about traffic congestion and are intended to benefit residents, traders and motorists.
"While only a very small percentage of tickets are actually contested through PATAS, they have been controversial and the council is concerned to ensure it is enforcing yellow box junctions appropriately across the borough.
"As this confused situation is clearly unacceptable, at the beginning of the
year we sought the DfT's views on the design of the yellow box junctions.
"Our decision to suspend enforcement of the yellow box junctions on South Road is to prevent any further confusion while we continue to await guidance from the DfT, but it does not mean people who have historically been issued with penalty charge notices will have their fines refunded."