Priti Patel has failed to adequately explain why Boris Johnson's landmark trip to Russia was cancelled at last minute's notice, the BBC's Andrew Marr has said.

The international development secretary appeared on Marr's flagship politics programme in the wake of a chemical weapons attack in Syria, which has been widely blamed on President Assad's forces.

Following the attack, Johnson confirmed his withdrawal from the trip in a statement which said he "deplored" Russia's backing of Syria. But it rumours persist he was instructed not to attend by his US counterparts.

Appearing on the show on behalf of the government on Sunday (9 April), Patel was repeatedly asked about the justification of Johnson's cancellation when a number of voices have said this is the time for increased diplomacy with the Kremlin, not the opposite.

When Patel was first asked about the cancellation, she said: "Well, it's quite clear that events with regards to Syria have moved on.

"Our focus and, rightly, the foreign secretary's focus is now working with the international community to look at a political resolution and so he's focusing on the G7 meeting that's taking this coming week and working of course with the US, but importantly other allies in the international community when it comes to finding the right kind of peaceful and political settlement to this conflict."

However, Marr – who could be heard impatiently interrupting Patel's responses with "sure" and "right" – said: "The problem, if I may say so, with that explanation is that we're saying now that the important thing is to talk, to negotiate, to get back to the negotiating table, above all with the Russians and yet at this moment, we chose not to go and talk."

In response, Patel said Johnson did not need to go to Moscow as US Secretary of State Rex Tillerson's visit in Russia was still going ahead as planned and that the voices of the international community would be delivered to Russia that way.

She went on to say that the British government was in communication with all its "international counterparts" as she repeated her earlier response. However, Marr repeatedly interrupted to say "Except for the Russians".

Marr added: "This is what is so bemusing. I'm sorry to go on about it, but we keep saying we must talk to the Russians – they're at the heart of the process – and yet, given the opportunity for a really big [and] important summit in Russia, we pull out right at the last minute.

"We offend the Russians. We don't know why we're doing it. We don't get a proper explanation of what's going on."

As Patel again attempted to say Britain was "engaging with all international counterparts", Marr could be heard mumbling, "Extraordinary," before saying: "I'm not sure we've made a huge amount of advance, but thank you very much indeed Priti Patel."