New Delhi, April 22 -- The former head of Britain's foreign service said Tuesday he was pressured by Prime Minister Keir Starmer's office to rush through the confirmation of Peter Mandelson as British ambassador to Washington, and claimed Downing Street brushed aside security concerns about the choice.

The testimony by Olly Robbins increases the heat on Starmer, who is facing calls to resign over the decision to appoint Mandelson, a scandal-tainted politician and friend of Jeffrey Epstein, to one of the U.K.'s most important diplomatic posts.

Robbins, the former top civil servant in the Foreign Office, said there was an "atmosphere of pressure" from Starmer's 10 Downing St. office to approve the appointment so Mandelson could be in the ...