Foxtons has been fined £35,000 for failing to prove to a local council that a house it was letting was safe for tenants.
Foxtons had been asked by the local authority in Tower Hamlets, east London, to provide safety documents for the property but failed to do so over an 18-month period.
A statement from the council says that a case at Bow magistrates court heard that Foxtons had ignored requests to provide certificates showing that the gas, electrical and fire alarm installations had been checked.
It had also failed to submit details of the landlord and details of the tenants to the council.
The court heard that although the house was believed to be in good condition, Foxtons' failure to comply demonstrated a lack of regard for its duty to comply with legal requirements.
Foxtons pleaded guilty and in addition to the fine it was ordered to pay £3,603 in costs.
The deputy mayor of the authority, councillor Sirajul Islam, said: “This case has sent a very strong message out to landlords and agents.”
Foxtons told the court it prided itself on its reputation as one of the county’s largest agents. It said it was ashamed and remorseful of the failings that led to the offence.
In sentencing, the court made clear that the fines took into account of the size of the company, its profits and the ease with which it could have provided the information to the council.
The charge initiated by Tower Hamlets council came under Section 236(1) of the Housing Act 2004: failing to comply with a notice served under Section 235 of the Housing Act 2004. This notice requires a "person with a relevant interest in a property" to provide documents to a council for any purpose connected with its housing enforcement functions.