The Government has a comprehensive range of powers to protect national security. Under the Enterprise Act 2002, the Government has the power to prevent relevant mergers and acquisitions concerning the UK’s critical national infrastructure on national security grounds.
In July 2018 the Department for Business, Energy, and Industrial Strategy published the National Security and Investment White Paper which sets out proposed reforms to the government’s powers to protect national security from hostile actors using ownership of, or influence over, businesses and assets to harm the country. These proposed reforms will address the technological and economic changes that have taken place in recent years, that have changed the types of national security threats the UK faces.
Depending upon the factual scenario, the Government may have other powers to ban or restrict a named company’s involvement as (a) a UK critical national infrastructure operator; or (b) a supplier to a UK critical national infrastructure operator. However, this will vary depending upon the specific critical national infrastructure sector in question and how it is regulated.
2018 White Paper: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/728310/20180723_-_National_security_and_investment_-_final_version_for_printing__1_.pdf