HM Treasury (HMT)

Role

Central government finance ministry. Sets fiscal rules; controls departmental budgets through Spending Reviews; owns the Green Book appraisal framework; co-published the 10 Year Infrastructure Strategy with NISTA; manages National Wealth Fund (£5.8bn for hydrogen, CCUS, ports, green steel).

Strategies owned

• budget-spending-review-2025 — Budget 2025, Spring Statement 2025, Spending Review 2025
• 10yr-infrastructure-strategy — Co-published with NISTA

Outcomes accountable for

• Fiscal stability (stability and investment rules)
• economic-growth-gdp — Overall growth mission co-ownership

Key commitments

• Stability rule: current budget surplus by 2029-30 (buffer: £15.1bn as of Spring Statement)
• Investment rule: net financial debt falling as share of GDP by 2029-30
• £725bn infrastructure over 10 years
• R&D £22.6bn/year by 2029-30
• £39bn Affordable Homes Programme
• Sizewell C £14.2bn

Green Book

Revised 2025-26: “radically shorter and simpler.” Provides the appraisal framework for all major infrastructure investment decisions — the analytical foundation for the £725bn programme.

Relationships

• Oversees NISTA; sets fiscal framework for all departments
• Works with DBT on Industrial Strategy
• Works with DESNZ and MHCLG on National Wealth Fund deployment
• Works with MOD on defence spending commitments

Tensions

• delivery-confidence-fiscal-ambition — Fiscal plans assume efficient delivery of £725bn; NISTA’s own data shows rising red-rated projects and cost inflation
• defence-oda-funding — HMT agreed to fund defence uplift via ODA reduction — an explicit cross-departmental trade-off