Angela Merkel is to meet bereaved relatives and survivors of last year’s Berlin Christmas market attack for the first time, two weeks after they sent her an angry letter accusing her of political inaction and failing to acknowledge their suffering.

The German chancellor will meet the group in her office in Berlin on Monday, a day before the anniversary of the attack.

Her spokesman Steffen Seibert said Merkel had felt “the greatest respect” on reading their letter, in which she was accused of a dereliction of duty. He said the victims’ outpouring of their grievances showed “how useful and urgent this meeting is”.

Twelve people died in the attack on 19 December, in which Anis Amri, a Tunisian whose asylum application had been turned down months before, drove a lorry at speed into the Christmas market on Breitscheidplatz. Almost 100 people were injured, many of them in life-changing ways. It was Germany’s first major Islamist-inspired terrorist attack.

The victims included the lorry’s Polish driver, whom Amri shot before he took over the controls. Amri was shot dead by Italian police in a suburb of Milan four days after the attack.

In the letter to Merkel, the victims set out a range of grievances over their treatment, including “the lack of counter-terrorism in Germany, as well as the way we as victims and bereaved have been dealt with”.

In the year since the attack, they wrote, “we note that you have not shared your condolences with us either in person or in writing. In our opinion this means that you have failed to live up to your office.”

They accuse Merkel’s government of failing to address systemic shortcomings that had allowed Amri, who arrived in Germany during the refugee wave in 2015, to apply for asylum numerous times and to remain at large despite the fact he had been classified by security forces as a high-level threat and had a criminal record for drug dealing.

“At a time when the threat posed by dangerous Islamists has greatly increased, you have failed to push ahead with expanding resources and reforming the confused official structures for fighting these dangers,” they wrote.

In what was widely interpreted as her acknowledgement of the grievances, Merkel visited the site of the attack last Monday, speaking to stallholders at the market and thanking those who had risked their lives to come to the aid of those hit by the truck and by falling debris.

The scene of the Christmas market attack on 19 December 2016. Photograph: Odd Andersen/AFP/Getty Images

“Frau Merkel has behaved shabbily towards us,” said Sigrid Rheinsberg, who lost her daughter, Dorit Krebs, 53, in the attack.

Her husband, Hans-Georg, said: “Frau Merkel embraced the refugees but has put us at arm’s length. We’ve been completely ignored.”

The couple told Der Spiegel they felt strongly that the German state was complicit in Amri’s murderous act. “The state should bear part of the blame,” Sigrid Rheinsberg said, referring to multiple errors made by the authorities. “It wasn’t the perpetrator, but it is complicitous.”

Rami Elyakim, an Israeli who lost his wife of 40 years, Dalia, and who was badly injured himself, said he had been appalled to learn of the catalogue of errors made leading up to the attack.

“An Islamist with 14 different names allowed to move about freely?” he said in an interview, referring to the authorities’ repeated failures to apprehend Amri. “They could have put him in prison or at least been on his trail.”

Elyakim said his medical treatment had been excellent but that he had received pitifully little financial support from the German state. He had had to depend on help from the Israeli state, which had acknowledged him as a victim of terror, he said. “Germany has done nothing,” he told the newspaper Bild.

Many of the victims say that on top of having to wade through a bureaucratic minefield, they have struggled financially and have received paltry compensation payments. Some have taken out bank loans to cover the rents and mortgages of those who died or on behalf of those so badly injured they can no longer work.

Almost all the bereaved complained that they had no letter of condolence from the German state and that the first official recognition they had received that their loved ones were dead was a bill from the institute of forensic medicine demanding a fee of €51, payable within 30 days, for certifying the cause of death.

“I didn’t want to believe it myself,” said Kurt Beck, an MP for the Social Democrats. “But I saw one of these letters with my own eyes.”

Beck, who was appointed as official representative of the victims and bereaved in February, acknowledged the catalogue of errors made by state organisations before and after the attack in a report published last week. He has recommended a long list of improvements, including better communication with victims and much higher compensation payments.

Most victims have so far received little more than €10,000, and only then after going through a highly bureaucratic application process. Beck said a department should be set up within the justice ministry to act as a coordination centre to deal with any future attacks.

“The government cannot leave the injured and bereaved to deal with the situation themselves,” Beck said. “What’s most important is to help them out in their hour of need, to not have them running from pillar to post trying to establish the facts and what they’re entitled to.”

On Tuesday, the anniversary of the attack, officials and survivors will gather to unveil a memorial to those killed. Relatives will be invited to fill with liquid gold a 14-metre-long gash indicating the path the lorry took, and symbolic of the scar that remains, according to officials.

The steps leading up to the Memorial Church, which was bombed during the second world war and remains in large part a ruin as a deliberate reminder of the horrors of war, will be engraved with the names of the victims and their countries of origin.