Senior executives from private security firm G4S are to be grilled by MPs over the "shambles" of its failure to honour its contract for London 2012.

Lord Coe, chairman of the organising committee in charge of the Olympic and Paralympic Games, and Scotland Yard chief Bernard Hogan-Howe will give evidence to the Home Affairs Select Committee about the debacle that led to troops being drafted in at the 11th hour.

The hearing comes the day after the final celebrations of the Games in central London, when thousands of people took to the streets to cheer as British athletes paraded through the capital in open-top buses.

The security fiasco on the eve of the Games was the only significant shortcoming in the organisation of the Olympics, which has otherwise been widely praised.

G4S chief executive Nick Buckles and David Taylor-Smith, the company's chief operating officer, will seek to limit the reputational damage when they are questioned by MPs.

Committee chairman Keith Vaz said he wanted to ascertain how the security crisis occurred and who was responsible. "From the evidence we have received so far the Home Secretary and the Permanent Secretary are very clear that G4S failed to honour their agreement to provide sufficient staff," he said. "G4S were unable to give us a convincing account of what went wrong when they came before us in July.

"We are looking forward to hearing from them again on Tuesday, when they will have had exactly two months to investigate what led to the shambles we witnessed just before the Olympics was due to begin. Everyone now accepts that G4S let the country down at a crucial time."

On Monday, Mayor of London Boris Johnson thanked G4S as well as the military, police and volunteers for their parts in the Games. But the company has already admitted it is fighting to repair its battered reputation after failing to provide all of the 10,400 contracted guards.

It fulfilled only 83% of contracted shifts at the Games. The Government put another 4,700 military personnel on standby, on top of 13,500 initially committed, after G4S admitted its shortfall in July. It has already ruled itself out of bidding for the Rio 2016 Olympics security contracts.

In a sign of the challenges facing the company, a police authority confirmed last week that it was pulling out of a privatisation scheme following the G4S failure. Surrey Police had drawn up a shortlist of six groups, including G4S, bidding to take over "middle and back office functions".