The Government's controversial part-privatisation of the Tube has been completed with the consortium taking over the remaining two-thirds of the system concluding its financial deal.

The Metronet consortium will invest £17 billion into London Underground over the 30-year contract, with £7 billion being poured in over the first seven-and-a-half years.

The other consortium - Tube Lines - took over the responsibility of the Underground's Jubilee, Northern and Piccadilly lines at the end of last year.

Metronet will now have responsibility for the remaining lines.

All 150 stations under its responsibility will have new closed-circuit television, public address systems and destination indicators installed.

After the first three years, more than 60 stations will be modernised.

The Metronet consortium is made up of shareholders Atkins, Balfour Beatty, Bombardier, Thames Water and Seeboard, which have each provided £70 million of equity.

Balfour Beatty chief executive Mike Welton said: "We are delighted to become part of the London Underground public-private partnership plan (PPP) and to be able to play a key role in creating a faster, safer, cleaner and more reliable system."

The Tube PPP has been pushed through by the Government despite much protest, with opposition being led by London Mayor Ken Livingstone and the capital's transport commissioner Bob Kiley.

Both have been concerned about effectiveness and safety but the Government has maintained the PPP is the best way of injecting cash into an ageing Underground system.

While Tube Lines and Metronet will be responsible for the infrastructure of the Underground lines, overall responsibility for the Tube will pass from London Underground to Transport for London (TfL).

As well as being responsible for drivers and the staffing of stations, TfL will ensure the infrastructure companies carry out improvements.