Officers from nine police forces are being drafted in to fill the gaps in Olympics security following the failure of G4S to provide enough security guards for the Games.

The home secretary, Theresa May, was forced to update MPs on the debacle on Monday as it emerged that hundreds of officers from forces across the country were being drafted in to work alongside the extra 3,500 military personnel.

Assistant Commissioner Chris Allison, the National Olympic security co-ordinator, said officers from Dorset, Surrey, Hertfordshire, Northumbria, South Wales, Strathclyde, West Midlands, Thames Valley police and Greater Manchester had been deployed to provide security at venues in their areas.

In Manchester police were forced to step in after only 17 of an expected 56 G4S staff turned up at an Olympic team hotel in Salford at the weekend.

A similar picture was emerging in the West Midlands, where the regional chair of the police federation, Ian Edwards, said the force had had to provide 150 officers a day to cover a hotel in Warwickshire where Olympic footballers were staying.

Edwards said: "The worst-case scenario is that we end up having to find another 200 officers for the security at the City of Coventry stadium, and we've yet to find out what the shortfall is in Birmingham. It's chaos, absolute chaos. You shouldn't lose your local police officer because of the Olympics. Communities are suffering because a private company has failed to deliver on a contract."

Clive Chamberlain, chairman of Dorset Police Federation, said that although the army had covered for the majority of the shortfall in G4S staff so far, police officers were now being dragged in to fill the gaps.

"On a daily basis it's a lottery as to how many staff are going to turn up. The best they have managed is 15% not turning up, and on the worst occasions they have been 59% down. It's a fiasco, it's an absolute debacle."

The crisis has led to growing pressure on G4S chief executive, Nick Buckles, who faces a grilling by MPs on Tuesday.

The Olympics minister Hugh Robertson said on Monday that Buckles should keep his job "for now".

Asked if the G4S boss should resign, Robertson said: "No, not at the moment. G4S remain an integral part of the security plan. The last thing we want is a loss of leadership."

Robertson said he believed the crisis over security had bottomed out and, pressed by members of the foreign media, who have arrived in London in large numbers to cover the Games, he denied the situation was a "national embarrassment".

"There's a scale from mild embarrassment to complete disaster and this isn't significantly embarrassing," he said.

He stressed G4S had only recently realised that it would be short of several thousand security guards.

"We are sure that G4S gave us the best information that they had at the time," he said. "So clearly for them it was as much a surprise as it was to us," he said.

Allison said the police were working closely with Olympics organisers Locog, G4S and the military and dismissed the suggestions that the security plan was unravelling, saying: "The plan is exactly the same as it was, it is just being delivered by different people. I went through the search regime at the Olympic Park this morning and it was everything you could possibly want."

The shadow home secretary, Yvette Cooper, has been granted an urgent question in the Commons to press Theresa May, the home secretary, on whether she can guarantee that 3,500 troops will be enough. She will also press her to explain when the Home Office knew about the problems, and who within the department was aware.