Former U.K. Prime Minister Gordon Brown described the president-elect as being able to bring "America together."
All official EU referendum campaigning has been suspended until Saturday.
The former Labour prime minister said his party's voters would help swing the Brexit vote.
The report covers British involvement in Iraq between 2001 and 2009.
"People have no confidence in Tory guarantees and they are absolutely fizzing about what looks like a preparation for a betrayal of solemn commitment made," Scottish nationalist leader Alex Salmond said
Rival campaigns neck-and-neck as former PM Gordon Brown sets out timetable for new powers