The UK Department for Transport has recently published the Accounting Officer Assessment Summary for the Lower Thames Crossing project. This assessment was jointly completed by the Department for Transport and National Highways, based on the decision in the Autumn Budget 2025 regarding project cost re-baselining and the preferred financing model. The Accounting Officer Assessment supports continued public funding for the tunnel project, while identifying the Regulated Asset Base structure as the preferred financing method. This model would primarily be funded through user charges and private investment to reduce direct risk to taxpayers.
According to the assessment, the government's spending commitment for the Lower Thames Crossing project will continue until 2028/29, with development consent for construction legally granted in March 2025. Regarding financing and risks, officials noted that the Regulated Asset Base model might keep the project off the government's balance sheet, avoiding direct public debt, but uncertainties exist and require further consultation with the Office for National Statistics. Additionally, implementing this model would require new legislation to establish a regulatory regime and charging powers.
The Value for Money analysis indicates that all three financing options—full public funding, a hybrid model, and the Regulated Asset Base model—have benefits exceeding costs, but fall into the low Value for Money category. The hybrid model performed weakest, while the Regulated Asset Base model's benefits are close to those of full public funding, although user charges may diminish its advantages. Officials emphasized the strategic importance of the Lower Thames Crossing, including alleviating congestion at the Dartford Crossing, improving transport reliability, and enhancing economic connectivity.
The assessment also shows that the project can proceed under either the Regulated Asset Base model or full public funding, with related work such as procurement restructuring and delivery vehicle creation currently underway. However, officials cautioned about delivery risks, including investor interest, charge levels, legislative requirements, and schedule pressures, which will be reviewed in future business case stages. The next steps include refining the Value for Money analysis and preparing a full business case, with further assessments expected.
