The grieving father of Harry Dunn, the British teenager killed in a hit-and-run, has issued a stinging attack on Dominic Raab, accusing the foreign secretary of “empty words” and meeting the family only as a publicity stunt.

Harry’s parents, Tim Dunn and Charlotte Charles, are campaigning for Anne Sacoolas, the wife of a US intelligence official who was allegedly responsible for the fatal crash, to be brought back to the UK to face justice after she fled to the US claiming diplomatic immunity.

In a comment piece for the Guardian, Dunn accuses Raab of being “cold, stiff and impersonal” when he and Charles met the politician in a “terrible” encounter set up under “false pretences” following their 19-year-old son’s death.

Dunn, who was dismissed by the foreign secretary when he confronted him last month outside a hustings in Raab’s constituency, condemned the politician’s conduct. “We think politicians should be honest and decent, and we feel Mr Raab is neither of those,” he wrote.

“He seemed really troubled to see me at the hustings. He was rude and dismissive, he pointed his finger at me. He could have easily pulled me aside and talked to me. If he didn’t have time to speak, he could have arranged for us to meet another time. Instead, he wouldn’t even shake my hand.”

The family, who plan to gather outside Buckingham Palace on Tuesday to “make our feelings known” to Donald Trump during his visit to the UK, first met Raab in early October.

Their son was killed two months earlier, outside RAF Croughton, in Northamptonshire, when his motorbike was involved in a crash with a car allegedly driven by Sacoolas on the wrong side of the road. Sacoolas returned to the US, but Charles and Dunn hoped Raab could push for her return to Britain. However, they were left disappointed after the meeting.

Harry Dunn death: a timeline of key events Read more

“Mr Raab was cold, stiff and impersonal. He offered his condolences, yet they only came across as empty words. The worst of it was that he didn’t actually have any good news: he insisted that Anne Sacoolas had diplomatic immunity. Charlotte, my wife, asked him if he would put in another request for a waiver and he said he would do that,” Dunne wrote.

“I had allowed my hopes to build up, and now I realised we had been brought in on false pretences. It felt to us like a publicity stunt so that Mr Raab could make it look to the public as though he was doing something for us. After we left the meeting, I broke down outside his office. I have been furious with him ever since.”

The Foreign Office said on Tuesday that Raab pressed the US secretary of state, Mike Pompeo, at a meeting in London to make sure that Sacoolas cooperated fully with British judicial authorities.

The UK says it is waiting to hear if the Crown Prosecution Service is to press charges against her over Dunn’s death, and says it cannot interfere in that process.

The Foreign Office said it believed that now that Sacoolas was back in the US she no longer enjoyed diplomatic immunity, and if charges were pressed she should fully cooperate with the British judicial authorities. Raab said the UK was doing everything it could to ensure that justice was done.

The parents accuse Raab of giving a statement to the House of Commons two weeks after their meeting with him that contradicted what he had told them.

“He said that on 8 October, the day before we met him, the US and UK had agreed that the question of diplomatic immunity was no longer pertinent because Anne Sacoolas had left the country. As a result, there were no longer any obstacles to justice. Why, then, had he told us that she still had immunity? When we heard that statement, we were horrified. After that, there was no way we could trust him.”

A further blow came, they say, when Raab told Sky News he was trying to clear the path to justice, despite having said a month earlier that there were no obstacles.

Having heard nothing from Raab since their meeting, the parents decided to travel to his constituency, Esher and Walton, to confront him. “If Mr Raab wasn’t going to let us know what he was doing, I wanted to ask him face to face, so he could explain all the lengths he had supposedly gone to,” Dunn said.

“We also wanted to meet local voters and let them know precisely what was going on. We think politicians should be honest and decent, and we feel Mr Raab is neither of those.”

Video footage of the encounter emerged showing Dunn politely approaching Raab as he arrived for the hustings. The politician claimed he was happy to meet but then dismissed Dunn, adding: “Not right in front of the cameras. It’s not on.”

In October, Charles and Dunn met Trump at the White House, where the president dropped the “bombshell” that Sacoolas was waiting in the next room to meet them.

The parents are suing the Foreign Office over its decision to advise police that Sacoolas had diplomatic immunity.

Dunn said: “All we want is for Anne Sacoolas to return so she can face the consequences of her actions that night when she took my Harry’s life, and for the truth in this whole mess to come out. I am not aware of a single cabinet minister who has called publicly for her to be returned. That is shameful. It’s hard to escape the conclusion that the British authorities care more about preserving the relationship with the US than looking after the rights of citizens like us.”