Canary Wharf Contractors has been working for 12 months on the foundations and basement slab for the Richard Rogers designed building.

But the whole future of the project has been thrown into doubt after JP Morgan raised concerns about London’s future as a world-leading financial centre.

Fears over a punishing regulatory regime for banks, uncompetitive tax rates for high earners and the impact of the new government’s austerity measures have led the bank  to question the development of its new HQ.

JP Morgan bought the site from the Canary Wharf Group (CWG) in 2008 for £237m. If it pulls out of the project at this late stage, CWG will be entitled to payment for work already completed.

If JP Morgan chooses to abandon the project entirely, Riverside South is expected to lie dormant until another large tenant appears on the scene because CWG will not build above ground level on a speculative basis.

JP Morgan has a loose deadline of the end of the year to make a decision.