Police in Glasgow and Manchester are to take on extra security roles at Olympic football venues because of gaps left by private contractor G4S.
Strathclyde Police informed the government that they "no longer had confidence" in G4S's ability to provide proper security arrangements.
And Greater Manchester Police will fill posts for fixtures at Old Trafford.
It comes after only nine G4S security recruits out of up to 140 attended a Manchester training session.
G4S would have been responsible for day-to-day security at both stadiums as well as training venues used by teams playing there.
Hampden Park and Old Trafford are two of the six venues being used around the UK for the Olympics men's and women's football tournaments.
Meanwhile, shadow home secretary Yvette Cooper is to write to Home Secretary Theresa May to demand "full disclosure" about events leading up to the G4S staff shortage.
Troops 'not needed'
Strathclyde Police's decision comes after the force said on Monday that extra officers were being drafted in because G4S confirmed it was not able to meet its commitments at Hampden Park and training venues in Scotland.
In a statement, Strathclyde Police said: "Following recent developments surrounding security arrangements for the Olympic 2012 events in Glasgow, Chief Constable Stephen House has decided Strathclyde Police will assume primary responsibility for security at Olympic venues."
The force said they did not envisage troops would be needed to bolster security - as in London, where 3,500 have been deployed so far.
A Scottish government spokesman said police informed ministers that they had lost confidence in G4S to provide adequate security for the matches or at hotels used by Games competitors and officials.
"They have therefore assumed primary responsibility for all aspects of Games security north of the border," the spokesman said, adding that the government welcomed the "decisive action".
Greater Manchester Police confirmed they had been asked to provide officers to fill gaps in security at Old Trafford for the Olympic men's football group matches.
Assistant Chief Constable Terry Sweeney said the move would ensure a "significant police presence" at the stadium from Sunday.
"There will be a minimal impact on policing the local communities that we serve on a daily basis," he said.
In other Olympics news:
- The Olympic flame has arrived in London, transported from Guildford by helicopter before an abseil into the Tower of London
- Sir Chris Hoy, four times Olympic cycling gold medallist, is considered the favourite to carry Team GB's flag in the opening ceremony
- London 2012 chairman Lord Coe has promised a "safe and secure Games" despite the security guards debacle, thanks to military and police assistance
- Home Secretary Theresa May said security was not being compromised as she visited the Olympic Park control room with Lord Coe
- A 17-year-old boy has been arrested after running out of the crowd and attempting to grab the Olympic torch in Gravesend, Kent, on the flame's route from Maidstone to Guildford, Surrey, on Friday
- Lord Coe has defended the Olympics' branding rules, which he admitted could see spectators banned from wearing Pepsi T-shirts and other items to events
- A human rights lawyer has said the authorities have "lost the plot" over the Olympics and are needlessly arresting people
On Thursday the home secretary said she was told of a "possible temporary shortfall" in G4S security guards for the Olympics on 27 June, not on 11 July, as she previously told Parliament.
In Ms Cooper's letter to Ms May, she says that with a week to go until the Games begin reassurance is needed.
The letter goes on: "Once the House of Commons returns in September, however, we will need full disclosure about the events leading up to the G4S problems, and Parliament will need to scrutinise in detail why things went so badly wrong.
"We will also need to know why you gave such an incomplete and selective account to Parliament, which gave people the wrong impression about what happened, and why you waited until after Parliament had risen to admit that the Home Office had in fact known about G4S problems two weeks earlier than you had said."
In the letter Mr Cooper urges full disclosure of the meetings and discussions that took place around G4S in the run up to the Olympics.