Police are investigating after a letter was delivered to the former Tory leadership candidate Penny Mordaunt threatening to “shoot her in the head”.

The death threat was sent to the constituency office of the Portsmouth North MP before she was voted out of the contest to be leader of the Conservative Party.

During her campaign, the trade minister had complained of opponents to her carrying out a “black ops” operation to scupper her chances.

The Portsmouth News reported that the letter included threats to “shoot her in the head” and “kill her family”.

A Hampshire police spokeswoman said: “At 11.50am on July 22, we received a report of a letter containing threats to kill a Portsmouth woman and her family which was sent to her office in Lakeside, North Harbour.

“We attended and safeguarding measures were put in place to minimise the risk to the woman and her family, employees and the wider community.

“Our inquiries into this incident are ongoing and it has been referred to the Parliamentary Liaison Team.

“We take the safeguarding of our MPs incredibly seriously and there are robust systems in place to ensure they can carry out their job safely.”

Ms Mordaunt’s office has been approached for comment.