Keith Anderson, the Spanish-owned firm's chief corporate officer, said the policy would sow "doubts and fears" about the sector.
In a letter to Ed Miliband, who set out plans last week to freeze gas and electricity prices for 20 months if Labour were to win the 2015 general election, Mr Anderson spelt out how this might affect plans to invest up to £15 billion in the UK.
This would include a proposal outlined to regulator Ofgem to spend £5.2bn on the firm's distribution network, a scheme that will play a major role in connecting renewable energy as well as improving reliability and service and reducing costs for customers.
The money would be in addition to the £2.6bn investment in the network between now and 2021. Together the projects would create 4500 new jobs, Mr Anderson said.
Mr Anderson acknowledged "understandable and widespread concerns about consumer prices" but added: "Any move to freeze domestic bills will not alter the fact that the investment Britain needs still has to be paid for.
"To the extent such a freeze would cause investors to doubt they will receive an adequate return or to fear future similar interventions, those doubts and fears would be reflected in the appetite to invest."
Mr Anderson hinted that investment by the company, owned by Spain's Iberdrola, could go elsewhere if the corporate climate in Britain were to change.
"We carefully analyse all of the major markets in the world. Maintaining principles of sound regulation and avoiding regulatory uncertainty are critical to securing this global investment in the UK."
Mr Anderson's explicit warning about the consequences of Labour's pledge is the latest alarm sounded by the energy industry, which has warned the freeze would hit the building of new power stations and affect 600,000 employees.