Crime in the capital is higher because police ICT systems are "out-of-date, ineffective and expensive to maintain".
Members of the London Assembly said officers "take a step back in time" when they go to work and that Scotland Yard faces "a huge challenge" in updating its technology while facing budget cuts.
However, the committee found that the Met, which is due to implement a new ICT strategy later in the year, understands the scale of the challenge it faces.
The report by the budget and performance committee said: "The Metropolitan Police Service faces a huge challenge. It urgently needs better information and communication technology (ICT); and it must reduce its spending on it.
"The problem is complex. The Met's current ICT is out-of-date, ineffective and expensive to maintain. The force has not had a coherent ICT strategy for years and senior leadership in this area has been lacking.
"The Met spends a lot of money on ICT, but most of it goes on maintaining old systems, rather than investing in new technology. Consequently, police officers lack the technology to do their jobs as productively and effectively as they could. Crime is higher as a result."
The report highlighted the fact that the mayor's office for policing and crime (MOPAC) has an unfilled vacancy for the director meant to oversee Scotland Yard's ICT, and said the committee is "not convinced" that it has the expertise necessary to fill the job.
"The Met has been paying over the odds for technology for years; spending much of which has gone on maintaining a collection of out-dated and increasingly inefficient systems put together over the last 40 years. This has got to change,” said chairman of the budget and performance committee John Biggs in his foreword to the report.
"At the end of the day, this kind of investment costs money and with plans to cut spending by 20 per cent over the next three years, MOPAC urgently needs to determine what resources will be available to the Met to improve its technology. The force simply cannot afford to get this wrong again."
But the report did praise the helicopter team's popular Twitter account @MPSinthesky as a good example of what can be achieved with social media.
It also suggested that the force looks at using crime mapping techniques – where historic data and factors such as the weather are used to predict where crimes are likely to occur – that have successfully been trialled in Los Angeles.
Biggs said: "Tablet and smartphone technology is commonly available and relatively cheap. Yet a police officer has to radio back to base to find out simple background information about, for example, previous crime reports or information about particular suspects.
"It seems incredible that officers have this modern technology at home yet when they arrive at work they take a step back in time."
He added: "Every other person has a smartphone in their pocket and yet the Met are only just starting to look at rolling out similar tools. They should also be working on predictive crime mapping, like that used in Los Angeles, to get officers in the right place at the right time to deter criminals and reassure the public.