Downing's The Capital has emerged as the strong favourite to pick up the 200,000 sq ft Home Office consolidation in Liverpool city centre.
Agents in the city say Downing is in advanced talks with the Government agency having overtaken Bruntwood's The Plaza as the likely choice for the new office base.
The deal could take up all vacant space in the 390,000 sq ft Capital, acquired a few years ago from Royal & Sun Alliance and still partly occupied by the insurer. Economic development agency Liverpool Vision is also a tenant.
The UK Border Agency requirement is to occupy up to 100,000 sq ft immediately and the remaining half within three years.
Downing has reportedly withdrawn from pitches for other live office requirements for fear of taking up space reserved for the Home Office department.
The UK Border Agency currently occupies space in Downing's Graeme House on Derby Square, as well as Reliance House and Martins Building, both on Water Street. DTZ is advising UK Border Agency. All parties declined to comment.