Liz Truss has claimed that the aggressive barking of guard dogs outside prisons could prevent drones delivering banned items to inmates.

Figures released earlier this year showed a big spike in the number of incidents of prisoners taking receipt of drugs, mobile phones and other banned products via unmanned aircraft. Some 33 incidents were recorded in 2015 compared with just two the year before and none in 2013.

The technological developments have posed a headache for ministers as they seek to keep the prohibited materials from entering prisons. To deal with the issue, Truss this morning claimed guard dogs could help deter the drones from advancing to their destination - by barking.

Speaking during Justice Questions, the Cabinet minister said the Government was reviewing measures such as extra netting, before adding:

“I was at HMP Pentonville last week. They’ve now got patrol dogs who are barking, which helps deter drones. So we are using all kinds of solutions to deal with contraband coming into our prison.”

Justice Secretary Liz Truss explains that patrol dogs "who are barking helps deter drones" pic.twitter.com/WZuJBuXW42 — Sean Clare (@Sean__Clare) December 6, 2016

As Truss made the point, her government colleague Sam Giymah, junior minister for prisons, struggled to keep a straight face.

The justice secretary then doubled down on the claim when teased by Tory MP Victoria Prentis, who asked: “What guidance and training are being given to governors to ensure that they are able to complete the procurement process properly, be it about mental health service provision, or even the recruitment of dogs that bark at drones?"

She replied: “I thank my Honourable friend for her question and it sounds like she’s asking for some of these patrol dogs at her local prison, HMP Bullingdon.”

The episode is the latest instance of the senior Tory not being taken seriously after attempting to make a serious point.

Truss is already struggling to live down a speech she gave at the 2014 Conservative conference when she was environment secretary. Addressing delegates on the topic of British food exports, she declared:

“We import two-thirds of our cheese. That. Is. A. Disgrace.”