Two UK-listed businesses yesterday opened the door to private equity takeovers threatening to deliver a £1billion blow to the City.

UK-listed Ashtead Technology said it had received a £500million offer from US private equity firm Ember Infrastructure Management.

City asset manager Pollen Street, meanwhile, said it had begun a strategic review which may result in it being taken private. The disclosures will renew concerns about the exodus of companies from the London market, further diminishing its standing as a global listing venue.

Ashtead Technology, founded in 1985, provides underwater technology for the global offshore energy industry.

It said it had received an unsolicited approach from New York-based Ember valuing it at 615p a share and revealed that it had followed three previous proposals, the first two of which were ‘unequivocally rejected’ by the board.

Under takeover rules, Ember must make a firm bid by October 21. Shares soared 60.3 per cent, or 205p, to 545p.

Pollen Street confirmed yesterday that it had begun ‘an assessment of strategic options’, with one possibility ‘for the company to be taken private’. Shares jumped nearly 12.5 per cent, or 102p, to 917p.