The Financial Conduct Authority (FCA) is the competent authority for listings. For listed companies, the UK Listing Authority (a division of the FCA) monitors and enforces compliance with the Listing Rules. The decision as to whether to prevent the trading of certain shares on the London Stock Exchange rests with the FCA and London Stock Exchange. The FCA has no power to refuse a listing for reasons of security or national interests. Under the applicable legislation, the Treasury has no power to intervene to block a flotation on national security grounds.
The Government operates a rule of law based system whereby sanctions can only be applied when clear criteria are met. Any additional legislation on listings on the grounds of national security would need to demonstrably add value to the Government’s existing powers.