Billionaire media mogul Michael Bloomberg has slammed the UK's decision to leave the EU and suggested that he regretted investing in a new European headquarters in London, it has been reported.

The 75-year-old opened the headquarters of the company bearing his name on Tuesday (24 October) but comments which he reportedly made in Boston earlier in the month appeared to question if he would have made the same decision to invest in the hub had he known the Brexit referendum outcome.

The Guardian reported that he said at the Hubweek technology conference how the company was opening a new European headquarters in London with "two big, expensive buildings".

"Would I have done it if I knew they were going to drop out? I've had some thoughts that maybe I wouldn't have, but we are there, we are going to be very happy.

"My former wife was a Brit, my daughters have British passports, so we love England...butwhat they are doing is not good and there is no easy way to get out of it because if they don't pay a penalty, everyone else would drop out. So they can't get as good of a deal as they had before," he said.

Bloomberg employs 4,000 staff in the UK which is the company's headquarters in Europe. The former mayor of New York said that some staff were concerned about their future in London because some felt that "this country doesn't like immigrants".

"I did say that I thought it (Brexit) was the single stupidest thing any country has ever done but then we Trumped it," he said according to the Guardian, referring to the US presidency race in 2016 which he contemplated joining as a third candidate before he ruled himself out.

"It is really hard to understand why a country that was doing so well wanted to ruin it. It was not a smart thing to do and getting out of it is going to be very difficult and is going to be very painful," he added.

However, at the London unveiling of the headquarters, Bloomberg, who is worth an estimated $47.5bn (£36.2bn) said his company was "strongly committed to London".

At the event attended by London mayor Sadiq Khan, he said: "Whatever London and the UK's relationship to the EU proves to be, London's language, timezone, talent, infrastructure and culture all position it to grow as a global capital for years to come."