In a statement released this morning, the mayor gave the green light to the vast proposals, which were drawn up by Allies and Morrison with Dimitri Porphyrios.
The scheme - which will involve a huge number of commissions for a raft of architects - will transform one of central London's most blighted areas. It won planning from Camden planners earlier this month ( Finally- Camden gives green light to King's Cross
Livingstone had been expected to approve the scheme at the MIPIM property fair last week, but last-minute negotiations with the Transport for London quango held this up.
However, all Argent now awaits before starting on site is an announcement from the Government Office for London that the scheme will not have to face a planning inquiry.
If the mixed-use scheme does get the final go-ahead it will involve the construction of nearly 2,000 new residential units. There will also be accommodation for up to 250 new businesses and a range of new community facilities.
Speaking this morning, Livingstone said he was delighted to be able to back the scheme.
'After many decades of decay we will start to see the rebirth of this crucial part of our city, he said. 'When the international rail terminus at St Pancras opens next year it will be a major gateway to London and the UK.
'The developer has responded imaginatively to this opportunity and to the challenges of this site by working closely with all stakeholders, including the Greater London Authority, the London Development Agency, Camden and Islington Councils and the local community, to ensure that we have a design of the highest quality.
'This is one of the largest sites still to be developed in central London, and I hope the development can now get going after so many years of planning,' he added.
Argent boss Roger Madelin was unsurprisingly over the moon. `Argent and our partners London and Continental Railways and DHL Logistics are delighted with the Mayor's endorsement for King's Cross Central,' he said.
'We will deliver a highly sustainable mixed-use development on Europe's most accessible transport interchange, with a real commitment to renewable energy and carbon reduction.
'We look forward to working with the London Development Agency, Transport for London and Camden and Islington Councils to deliver 25,000 new jobs, nearly 2,000 homes, new shops and cultural, leisure and community facilities to transform King's Cross and benefit the whole of London.'