Prime minister says kingdom provided intelligence that saved British lives after criticism of decision to fly union flags at half mast

David Cameron has defended the decision of the British authorities to fly the union flag at half mast after the death of King Abdullah of Saudi Arabia on the grounds that intelligence from the kingdom has saved British lives.

In an interview with young voters on Sky News, in which he was pressed about the decision to lower flags as a mark of respect to the late king, the prime minister initially spoke of the links between the two royal families.

But, pressed by Franchesca Hashemi, Cameron said Saudi Arabia had provided a vital piece of intelligence – a reference to a tipoff from the kingdom in 2010 which led to the interception of a bomb hidden in a printer cartridge on a cargo plane at East Midlands airport. The bomb had been deposited at the UPS office in Sana’a, the capital of Yemen.

Cameron told Hashemi on the programme Stand Up Be Counted: “I can tell you one time since I’ve been prime minister a piece of information that we’ve been given by that country has saved potentially hundreds of lives here in Britain.

“Now you can be prime minister and just say exactly what you think about every regime in the world and make great headlines and give great speeches but I think my first job is to try and keep this country safe from terrorism.

“If that means you have to build strong relationships sometimes with regimes that you don’t always agree with, that I think is part of the job and that’s the way I do it and that’s the best way I can explain it.”

Government buildings flew the union flag at half mast for 12 hours on the day of the death of the king last month on the instructions of the Department for Culture, Media and Sport, which said it was acting in line with protocol for the death of a foreign monarch.

The Houses of Parliament and Westminster Abbey followed the government guidelines.

The prime minister said on Sky that it was right to show respect to the late monarch.

But Hashemi asked whether the lowering of the flags was not “disrespectful to the people who the Saudi King has sentenced to a thousand lashes” – a reference to the Saudi blogger Raif Badawi.

This prompted Cameron’s remarks about co-operation on terrorism.