David Cameron has personally intervened in a last-minute attempt to provide a commemoration at the opening ceremony of the London Olympics for the victims of the 1972 Munich massacre.

The Prime Minister told the JC he was sympathetic to the idea of holding a minute's silence but thought it was unlikely at this late stage, and that the decision lay ultimately with the International Olympic Committee. On Wednesday, however, Downing Street began 11th-hour negotiations with Locog (the organising committee) to see if it could be persuaded to change its mind and provide a commemoration.

Mr Cameron went further than London Mayor Boris Johnson in his attempts to secure a commemoration. Mr Johnson initially said he would throw his weight behind the moves for a minute's silence. He then backtracked after taking part in a surprise ceremony organised by IOC president Jacques Rogge in the Olympic Village on Monday. Describing this event as "an appropriate, heartfelt observation of remembrance", the Mayor, who helped to unveil a plaque in Hackney in memory of the victims on Sunday, made it clear that he would not be pressing for anything further.

Two of the Munich massacre widows, Ankie Spitzer and Ilana Romano, who came to London to make one last plea to the IOC, expressed outrage at Mr Rogge's impromptu silence, staged in the Athletes' Village. "It's very cynical. It's like he was hijacking it," said Mrs Romano. "He felt that his house was shaking so he improvised."

"They had a quick small ceremony so they could say 'we did it'," said Mrs Spitzer.

But Mr Johnson said it was "an honour to be part of the IOC's moment of reflection".

Meanwhile, government departments attempted to deflect blame for the row onto the IOC. A Foreign Office statement said: "The minute's silence is a matter for the IOC. The UK recognises the importance of remembering the tragic events of the Munich Olympics. The Secretary of State for Culture, Olympics, Media and Sport will attend a ceremony at the Guildhall to mark the 40th anniversary - a joint initiative between the Israeli Embassy, Israeli National Olympic Committee (NOC) and the Jewish community."

As the days counted down to Friday night's Olympic Games Opening Ceremony, international pressure turned up the heat on the IOC and Mr Rogge, to no avail. President Obama threw his weight behind the campaign.

On Sunday a plaque honouring the 11 Israeli athletes was unveiled near the Olympic Village, in an art gallery near Hackney Town Hall. The plaque was the initiative of Linda Kelly, a Conservative councillor in Hackney – a designated Olympic borough - and Martin Sugarman, who chairs the Hackney Anglo-Israel Friendship Association, and its unveiling took place in the presence of the nephew of one of the murdered athletes, Yosef Romano.

Other guests included representatives from the Israeli embassy, former Olympian Ben Helfgott, Efraim Zinger, who is leading Israel's delegation to the Games, actress Maureen Lipman and Communities Secretary Eric Pickles.

Mr Pickles said it was a great pleasure to be associated with the plaque. "It must have been a little bit like this before the Munich Games, such hope and excitement. Yet it was not the images of records being broken that we think about Munich, or of great sporting triumph, it's a gunman in a balaclava standing on a balcony at the very heart of the Olympic village.

Members of the public are due to gather in Trafalgar Square in central London on Friday at 11am. Organisers have asked people to bring Israeli and British flags "or, indeed, [the flags of] any other country, because such a mix indicates international support".

The organisers stressed that it was not a political rally for Israel. "It is a short ceremony to commemorate publicly the murder of 11 athletes by terrorists 40 years ago, to remind people that this atrocity occurred and to honour the memory of those who were killed - something the IOC has refused to do."

Also on Friday, the Zionist Federation will hold a "virtual commemoration". Its "Minute for Munich" drive asks people to "make their own personal commemoration of the tragedy" by holding their own silences at 11am.

The chief rabbi has issued a prayer to be read on the first Shabbat of the Olympic Games in memory of the Munich victims. Synagogues around Britain will be able to recite it on Shabbat - the day before the ninth of Av, one of the most sombre days in the Jewish calendar - to mark the 40th anniversary. The prayer reads: "At this time in the Jewish year, when we remember the destructions of our holy Temples, and the many tragedies that have befallen our people throughout history, we mourn their loss and continue to protest against those who hate our people."

Earlier this week it was revealed that Germany received a tip-off from a Palestinian informant in Beirut that Palestinians were planning an "incident", three weeks before the 1972 Munich murders. In a story published on Monday, Der Spiegel claimed that the tip-off, originally given to the Foreign Ministry in Bonn via the German Embassy in Beirut, was taken seriously enough to be passed onto the secret service in Munich, who were urged that "all possible security measures" be taken.

However, the Munich authorities failed to act in response, and have never acknowledged the tip-off in the last 40 years.