A former top civil servant says a British exit from the European Union is not inevitable, although voters backed that course in a June referendum.

Prime Minister Theresa May has said Britain will open negotiations next year with EU partners to leave the 28-nation bloc following the public's 52 percent anti-EU vote.

But Gus O'Donnell, who was U.K. cabinet secretary from 2005 to 2011 and today sits in the House of Lords, says Britain could remain within a reformed EU following talks that would take "a very long time."

He was quoted Saturday telling The Times newspaper that a British exit "depends on what happens to public opinion and whether the EU changes before then." He says Britain could stay within a "broader, more loosely aligned" EU.